well... obviously message cannot be too specific and you seem to take it literally (too literally).
message point to an effect and not the cause of the problem. it tells that problem is detected in some circuit but it cannot identify individual circuit components that have failed. so thyristor may not be the one (or only one) component that needs replacement. and if actual cause is not removed you can continue blowing up things...
i have seen this error only once. in this case E1 motor was connected incorrectly to amplifier in KPP1. user was able to mate motor cable connector with motor in wrong orientation... once the initial misaligned orientation was set, it was no detectable difference during tightening connector. this created short circuit and KPP was destroyed. guess what happens if KPP is replaced without correcting wiring.
but this may not be your scenario, maybe some KSP is damaged and that resulted in KPP taking hit too.
simply swapping drives may leave you with bunch of damaged units and not cure problem. it is up to training and experience of technician to determine and remove real problem cause.
