diy-offgrid

I think that is about right. While I do not know the infini menu settings , I can tell you the following:
1. The infini has a bidirectional power chain, but its half duplex . Think about the load and grid on top of the chain, the battery at the bottom of the chain, and the pv somewhere in the middle. 
2. If you want to charge the  batteries from grid, power must flow from grid downwards to the battery.  
3. If you program the output source priority to use solar for the loads, then the direction of powerflow is from pv (the middle) upwards to the loads. Now because its a half duplex flow, you cannot have both directions at the same time.  Therefore the grid cannot charge the batteries. If there is excess pv though, it can flow downwards ti battery at the same time pv flows upwards to the load. 
4.So if you have pv, but you want the grid to charge the battery along with the pv, then you must tell the inverter to carry the load via grid as first priority and then pv. This releases the pv flow upwards to the load, frees up the flow, and the grid can now flow downwards and charge your battery. 
 
 
If you dont follow I will create a diagram  on request.