Saul

Thanks for sharing @Boerseun.
Since my one battery was replaced, my readings have been consistently at about 91%, which is equivalent to the 10000Wh you were originally getting. This is on discharging - when charging the implied capacity is pretty much at the expected 11kwH.  This is perhaps consistent with your experience - perhaps you are still getting less on discharging? Or maybe the higher than 11kwH on charging you are getting is consistent with 11kwH on discharge. I'd be interested in knowing this. 
As mentioned before, I would have previously written this off as efficiency loss - about 10% ,except for the fact that others with the same inverter were getting the full capacity on discharge (both with Hubbles and other batteries).  But I accept your point that there may be other factors which can affect this number. Overall, I am very happy with my installation - I can live with what may be slight underperformance or a less than optimal setup - I will just watch the battery performance closely to see if it deteriorates (or improves)!
 
 

@Brani @ThatGuy 
So, my new battery was ready on Tuesday as promised. My installer could only collect and install today. He told me when he arrived that Hubble had confirmed that the old faulty battery apparently had an inactive cell, which is why they replaced it. So, a definite positive there as they provided an entirely new battery -  only downside was the time to replace - as mentioned before, I have some sympathy given current circumstances, but felt the communication could have been better. Of course, the faulty cell is also slightly concerning, but apparently this is very rare.
As it was only installed today, I have had limited time to assess new performance. However, on limited data (using the method I described before), the 2 batteries I have look like they are performing at about 1kwH per 10%. This is better but still at only about 91% of expected performance, main caveat being the limited time to assess performance and reduce the effects of rounding.
I will monitor this more closely over the next few days to get a better handle on it and report back.

Update: 
I have monitored my system over the past few days with the replaced battery and I am still getting about 1kwH per 10% sometimes fractionally more. So I'd say about 92% of label capacity. This is mildly disappointing but probably only because other members have shown better performance with both their Hubbles and other brands. Prior to knowing that, I would have written it off as efficiency losses or Sunsynk measuring inaccuracy. If there are other Hubble owners out there getting similar performance, please let me know!  I'm not going to lose any sleep about it though but will watch it to see that it doesn't deteriorate (or at least, not quickly). Of course, if anyone at @HubbleLithiumhas any thoughts/comments on this, I would appreciate hearing them.
In terms of the overall post sales service from Hubble - I would probably say that it was on average positive. I never dealt with them directly, but their willingness to replace the faulty battery entirely was appreciated. There was a delay in the process as mentioned before, which was not great, but I am willing to accept that there were mitigating circumstances. I have not had any experience with other solar-related brands so I cannot compare Hubble to them.
 
 

@Brani @ThatGuy 
So, my new battery was ready on Tuesday as promised. My installer could only collect and install today. He told me when he arrived that Hubble had confirmed that the old faulty battery apparently had an inactive cell, which is why they replaced it. So, a definite positive there as they provided an entirely new battery -  only downside was the time to replace - as mentioned before, I have some sympathy given current circumstances, but felt the communication could have been better. Of course, the faulty cell is also slightly concerning, but apparently this is very rare.
As it was only installed today, I have had limited time to assess new performance. However, on limited data (using the method I described before), the 2 batteries I have look like they are performing at about 1kwH per 10%. This is better but still at only about 91% of expected performance, main caveat being the limited time to assess performance and reduce the effects of rounding.
I will monitor this more closely over the next few days to get a better handle on it and report back.

@Brani @ThatGuy 
So, my new battery was ready on Tuesday as promised. My installer could only collect and install today. He told me when he arrived that Hubble had confirmed that the old faulty battery apparently had an inactive cell, which is why they replaced it. So, a definite positive there as they provided an entirely new battery -  only downside was the time to replace - as mentioned before, I have some sympathy given current circumstances, but felt the communication could have been better. Of course, the faulty cell is also slightly concerning, but apparently this is very rare.
As it was only installed today, I have had limited time to assess new performance. However, on limited data (using the method I described before), the 2 batteries I have look like they are performing at about 1kwH per 10%. This is better but still at only about 91% of expected performance, main caveat being the limited time to assess performance and reduce the effects of rounding.
I will monitor this more closely over the next few days to get a better handle on it and report back.

Hi @ThatGuy
I was hoping to be further down the resolution path before providing feedback. This is where I stand at the moment (please note that all communication with Hubble has been done by my installer):
- Hubble agreed to swap out the battery that they initially thought might just be the BMS. This is obviously a positive. However, they said the new battery should be ready early last week, but then on Wednesday said it had been delayed until early this week (but based on other threads I've seen, this seems optimistic). They did not confirm what the problem was with the initial battery.
- I will hopefully be in a position by the end of this week to provide feedback on the new battery performance (providing I have it reinstalled in the next day or two - which as mentioned, seems unlikely now).
- My existing battery continues to run at about 88% of expected capacity. I have asked my installer to convey this to Hubble but I'm not sure how strongly he has made this point to them. Once the new battery has been installed, we will see if this affects the existing battery (I'm not sure if the BMS has been affected by the old misbehaving battery). I know @HubbleLithium check this forum from time to time, so I've included them on this response so that they are aware that I have a concern (as do others) that their batteries are running below the expected capacity. 
So, my battery was returned to Hubble on 21 April, which means I have been without an item I paid around R25k for, for almost a month. I have moved from mildly annoyed to annoyed. Needing to tiptoe around my limited battery capacity with the new bout of loadshedding has not made me happier. As I mentioned before, I can accept that problems arise with any product, and even that there are issues around global supply of components, but the lack of clear communication and expectations management is disappointing. 
I will provide further feedback when appropriate.