Qt Creator is extremely unstable

I experience crashing of Qt Creator several times for a couple of hours.
My project is qbs project.
The situation is very various:

• When opening a file
• When saving a file
• When changing project option
• When changing filename
• When adding new file
• When editing .qbs file

Basically, I think any kind of modification could cause crash.
I think searching never caused crash.

I cannot find the condition to reproduce the crash because the crashing goes away when restart Qt Creator.
For instance, after crash of Qt Creator when opening a .ui file, I execute Qt Creator again and then Qt Creator opens the very same file without any problem.

Please let me know if you need any information to fix this.