Were you able to open the project with previous versions on the Samba share? In other words, did the error start happening only after the update to 1.6 or did it also coincide with you moving the project to the shared drive?
Did Tropy update itself or did you update by installing the latest version yourself?
After the error happens, can you select Help -> Show log files from the menu and post the full tropy.log here? That might help us see what’s causing this.
In general, opening a project file from a Samba share should be fine. However, the read/write speed of the project file has big performance implications, so typically it’s better to keep the project file on a local drive; the location of the photos themselves has less of an impact.