"Can't Save" widget is popping up frequently

I just brought up the project, went into one blueprint and added one bool variable. then the following message popped up when I tried to save:
The asset ‘/Game/Client/Blueprints/MikaboshiGameInstanceBP’ (MikaboshiGameInstanceBP.uasset) failed to save.

Cancel: Stop saving all assets and return to the editor.
Retry: Attempt to save the asset again.
Continue: Skip saving this asset only.

I mean one change and a bug in saving pops up?