Two comments on this - having also had issues due to the supply volts to the Charge4 dropping excessively. I have a (filament) landing light and tests showed that that was causing low volts at low engine revs, but I have overcome that by some improvements to wiring configuration and connections/earthing. However, another cause of low volts that I still have to live with is due to the current draw for the electric flaps - which of course tend to be deploying while engine revs are also low. Not sure if the OP here has electric flaps?
There have also been questions here about "UPS" - I had fitted a 5Ah RS powerbank between the Charge4 and the PAW (mainly to allow the PAW and tablet to get up and running and all looking happy before getting as far as engine start, though also to provide power continuity if the flap current caused the Charge4 to temporarily shut the port ), having understood from the RS website that the device would function as a UPS. But that was not successful - the RS battery just ran down as it did not accept input current while it as giving output current, so every few flights I had to take it home and charge it up despite it being connected to the Charge4 while flying. On the suggestion of a pilot mate I then bought a Zendure A2 battery - and that really does operate like a proper UPS, maintaining a steady output to keep the PAW running irrespective of whether the Zendrue was being charged by the Charge4, or whether the Charge4 port was for whatever reason offline and no current was feeding the Zendure, and no sign of any hiccups on the output when the input changed from one state to the other. So for me it has proved an ideal solution.
BTW - until reading it here, I did not know that there was any benefit in using ports 1 or 3 on the Charge4 to mitigate any supply voltage dips - I had assumed all ports were identical. The fact that 1 & 3 will work from supply voltages down to ~9.9V whereas 2 & 4 need ~10.15 is useful; also the tip that the ports power up in the sequence 1,2,3,4 could be useful in some situations. Perhaps those details could be added to the user Manual in a future edition?
Stu