Two issues with Extended Tags

After using Extended Tags/Add field... button/Right Arrow button/Reset Fields... - ACOUSTID_ID field appears in the list twice instead of one ACOUSTID_ID and one ACOUSTID_FINGERPRINT (both should be there according to the post at Add mappings for more MusicBrainz tags)

Additionally, I am receiving this weird error:

This message appears after going to Extended Tags/Add field.../Dropdown button and pressing alt+tab.

The message can also appear twice, if you do the following: After going to Extended Tags/Add field.../Dropdown button, this time hovering over any tag field (not clicking anything) and then pressing alt+tab.

Thank you for looking into this , much appreciated!

I just reset the field list and I see only ACOUSTID_ID once, not twice.
I tried to reproduce the other behaviour:
Selected 1 track
Pressed Alt-T -> Extended tags opens
Click on Edit button -> Edit tag information opens, focus is on tag data, whole tag data is selected.
Press down arrow -> selection disappears, write cursor moves to the end of the data (as it is a single line of data)
Press alt-tab -> next application gets the focus (here: desktop)
Press alt-tab again -> Mp3tag's edit tag data dialogue gets the focus again, write cursor still at the end of the tag data.

How did you manage to open the extended tags dialogue again? Even though it is still open, the edit tag data dialogue has locked the rest of MP3tag.

Oh, I used the first "Add field..." button, not the second "Edit field..." button in the Extended Tags window. Both of the windows are showing the "Edit tag info" in the header text. I also clicked on the dropdown button (the arrow pointing downwards), not pressing the actual down arrow button. I apologize for the confusion. I edited my initial post.

Edit: I can also reproduce the bug when using the "Edit field..." button, but I need to remove the text from the "Field:" field before clicking on the dropdown arrow.

OK, so it is "New".
I clicked on "new" -> Edit tag field dialogue opens, focus is on empty field list.
Click on the combo box opener
Press Alt-Tab to switch to any other application
Press Alt-Tab again and get the error message that this is no valid parameter as an input for a tag field name was expected.

But I still do not get the edit dialogue twice.

I am not opening the edit dialogue twice, the second repro steps is for the same bug, but the other time it shows the error message twice, I will clean up my initial post once again.

I could reproduce to get the error message twice in a row after opening the dropdown list and hovering over an entry and pressing Alt-Tab so often that I return to MP3tag.

I also noticed that after closing the second error message, the edit dialogue only got the focus back when the mouse cursor was moved to the field selection combo box again.
Even though this is not the most elegan behaviour, it still does not lead to invalid data as you cannot input anything until a field is selected and some data has been entered.