Hi all,
Just an update on this - my Pylontech battery was eventually returned to SegenSolar and put through the RMA process.
They found a swollen cell and asked me if I wanted a replacement or cash back. I took the replacement - currently waiting for the new one to come back.
This was the battery with the high cell voltages as well as the massive SOC dips recently. The other two have been running my house since, and other than the fairly low 89% SOH (at least in my books) they’ve not given me any issues.
Will update once I have the new one installed!
@JacoDeJongh thanks for the help on this! If there were any fuss from Segen/Pylontech I never knew about it 
@Eskom thanks for keeping the lights on just before the election so that I could replace my battery 