SU3700E started to trip RCD

Have a Solax SU3700 connected to East / West arrays, been running for over 2 years without issue. Today system started tripping supply RCD. After reset system stayed on for a short while, but eventually tripped, reset after a period, but no tripping when arrays are initialised. Tried arrays 1 at a time, trip occurs on CH1, swapped arrays, trip remains on CH1. If only CH2 connected with either array, unit runs fine.

No errors in log, other than grid fail which would be expected.

There have been no hardware/firmware changes.

Any pointers on which components could be creating earth leakage fault?