Minimized window will not restore anymore

I installed the new SourceTree 3.0.6 (and then 3.0.8) on my machines and I am seeing a consistent issue on all.  I usually keep SourceTree always open and minimized.  The 3.0.x version will not restore anymore if left minimized "for some time".  It will restore if done shortly after minimizing, but after some undetermined time (minutes), it will get stuck minimized and I have to kill the process and restart it manually. 

This is quite an annoyance restricting the use of 3.0 so would be great to get fixed.