Existing exception days are being removed when adding new ones

I am making a mess...

Actually, a lot is broken, but this, I cannot replicate.
There is a problem with the form state: If you set the exceptions as collapsed, in the widget settings, the exceptions block is collapsed after [Add] button.
There is also a problem with the links and hiding slots.

Can you give some exact examples?

I'm working with the latest dev version (1.x-dev#46acef27) and can not reproduce either.

I guess there was an intermediate commit provoking this. I also had some corrupted data. Not anymore.