With great reluctance i think so. Other than replacing the board i'm out of trouble-shooting steps, and i have spent probably 6 days on it, and i'm driving a 5m camper van as the daily and its wearing a bit thin in this weather.
I really have no idea what has gone wrong, other than by a process of elimination it must be the board, and as a solution with the smt soldering required i'm not convinced a replacement in my hands would be any better and lead times are long and not cheap. The rear inverter was £90 and may well drive better anyway. it'll be interesting to see, i always felt the prius inverter was holding back a bit.
It's a shame, i was proud of having got that on the road, but it just went into a gradual decline. who knows, the new approach might not be the answer. time will tell, hope to have a bench test rig running this weekend, and with a fair wind get it in the car a week later as not much needs changing and my prototype junction strips make rewiring a doddle.