I hope they’ll get back to you soon. Haven’t seen a similar issue on the forum yet.
but it doesn’t sound like a problem with the modules then if both of them are “stuck” in one direction.
You could swap the z-axis modules and y-axis modules (don’t have to unmount anything, just switch the cables coming from the modules.
If the problem then also switches from one axis to the other you know for sure it’s not the module but either it’s in the controller or on of the splitters. Which you can swap as well to determine if it is one of the splitters. I think I do remember one issue of a bad splitter on the forum.
edit:
There seem to be some similarities with this topic. But the end conclusion/solution was never posted: