I’m also a vivid user of the ZAppLink (to use with Photoshop Elements) and I don’t notice anything out of the ordinary.
This is probably not what’s causing you issues but I still wanted to mention it because I got confused by this at some point myself: are you sure you’re editing the right layer(s)? Because I noticed that if you add layers or edit the wrong ones then this can result in ZBrush not picking up any changes.
And well… sometimes it can be easy to overlook.
Hope you can solve your issues!