Hi Hivez,
I am not sure but I think your issue could be linked to mine, it sounds like it because your issue happens on legato playing (overlapping midi notes). I created another topic about my problem with stuck midi notes since I am not totally sure if these issues are linked. Here is link to my topic/issue and findings on what exactly seems to cause it: Scaler 2.0.7 Overlapping midi notes causing stuck/hung notes