The response from the OEM technical staff I quote : 

First mail

The best would be to get the battery to us in order for us to investigate the problem.

Second mail after I told them I'm running without BMS

 Please note that you should not run without a BMS as this would damage the cells and has voided your warranty on the cells.

Is this a fact? this is the answer I received from my battery OEM, however, I don't see anything regarding this subject on they operating manual.

I have a cell on my battery that it's voltage is running lower than the other 15 cells.

Typically they customer service in my point of view is equal to  Zero, nada, niks. they told me, bring your battery over and we will tested. A reputable company would say I will send one technician to come and test it.

Further more the OEM technical adviser tells me to charge my battery cell to 3.6 V is this right? they manual recommends I add  states bulk charging voltage 56 V that equals = 3.5 V per cell. To achieve that cell voltage level I would have to change the the bulk charge to 56.7 V, than for sure I would be void the warranty.

See attached dashboard of my problem.

 

Would help if you told us what battery it is.

Personally I wouldn't run any without the BMS connected to the inverter and yes it probably does void the warranty, sure it says that for mine.