Jon, I am not Bartok user so I cannot answer your question directly. However I noted that you use an Amplifi mesh system. I recall that the use of mesh systems have from time to time caused difficulties reported here. I hope that @Anupc might pick up on this as he may be able to talk you through some of its settings.
I have experienced a dCS product ( not Bartok) “freezing” but this did not occur in-track.
There is also the oft visited question of the UPnP server software. This will probably not affect the “freezing” issue but could realate to the other issues that you cite.
NB: @Ermos reports that Asset works fine as well.