external FX inserts panel bug?

Hello

Cubase 7.5.20 x64 / Win7 x64

I use some external FX’s put in Audio Inserts of a Battery4 track (left panel on main screen). Randomly the object (external plugin) becomes inactive in left panel, even if i clean whole rack of this track and re-add any insert FX, no matter VST or External, it is still unusable and inactive. It can’t be turned on or opened to edit. The only solution is to restart whole Cubase.

Seems to be a bug, because my whole system is pretty stable

Please try to replicate it and provide a hotfix

thank you