Plugin do not save Primary Method changes

I found a working way:

1. Activate only the desired primary method and set it up
2. Select that method as primary method (keeping it at “default” won’t work)
3. Save
4. Set up other methods
5. Save
6. Activate other methods
7. Save
8. Check if the dropdown still has your primary method selected
9. If not, reselect and return to 8.; otherwise you’re done

That default option should just not be there, it doesn’t even have a value.