Yes, that sounds like the Stacks plugin is getting stuck on a file 
Feel free to send over the project file and I can take a look at it (no promises I’ll be able to find the culprit, but it’s worth a shot) - dan@realmacsoftware.com
Unfortunately the Stacks plugin hasn’t been updated in over a year, so I wouldn’t hold your breath for a fix 
There are some details here on how to contact YourHead. Would be worth dropping them an email as they are much more likely to know what’s going on with updates and fixes. Keep us posted if you hear back!