I bought an 1D4 mobo from Vesalia. Whether this has timing fixed or not, I don't know. After getting the ACA1231, the card works for 15-20 mins after which the Amiga can't boot anymore without getting a guru.
It was clearly an overheating problem. After buying a slim 80mm fan and jamming it next to the card in the trapdoor slot, the Amiga no longer crashes and can run for hours on end with the ACA1231, so some air circulation was all it was needed it seems. Not the best though, cause I hate the noise the fan makes. But I don't see what else I can do about it.