The Process Fields panel allows a state that makes no sense and disallows states that make sense. I think the root of this has to do with a bug in how this panel implements ghosting/unghosting various radio buttons in an attempt to disallow invalid choices to the user.

Steps to reproduce:
1. Open EasyTAG and open the Tag and Filename Scan window then select the "Process Fields" tab. It doesn't matter if any audio files are selected or not, you're not actually going to change any files.

2. Uncheck all of the Tag Fields -- Filename, Title, Artist, etc. and now you should not be able to make any changes to the other sections of this panel because you haven't specified which fields to apply them to. However, the other sections (Capitalization, Spaces Conversions, and Character Conversions) remain fully selectable. This is the allowing odd state bug.

3. If you check any Tag Field (say, "Title") the other sections become almost entirely unselectable. Only the last radio button in each group is selectable. So now you can specify "Do not change capitalization", "Do not change word separators", and "Do not convert". This is the disallowing valid state bug because at this point I should be able to pick any modification I wish.

The valid state bug is easily worked around -- pick another Tag Field and then unpick that same Tag Field -- and now the panel is fully available.