It appears you have a better than average understanding of soft starter and thyristor technology. I wander if we should we change your user name to SCR?

Back to the issues however. You mentioned that Company A is threatening to sue you. On what grounds? Or are they just trying to call your bluff?
You also stated that they have stopped responding to any of your questions. Gee, that sounds like a fantastic way to deal with an issue

It might be time you found yourself a supplier opf soft starters that understands issues and can provide the support you need. Have faith, they are out there.
Regards,
GGOSS