Debug regex help

Support
1

I'm using a couple of regular expression without being well-versed which means I can't figure out why I'm getting this result and I would really appreciate some assistance.

This is my mp3tag-action:

Replace with regular expression
Field: Performer
Regular expression: ([-({ _.+\x{201c}"])(\l)(?# for tags)
Replace matches with: $1$upper($2)
Case-sensitive comparison checked

Replace with regular expression
Field: Performer
Regular expression: (?<!&|:|;|-|/|!|\.|\?|\+)(\s+\b(A|And)\b)
Replace matches with: $lower($1)
Case-sensitive comparison checked

Something in this expression causes the following error in Musicbee: https://i.imgur.com/5MrWsEO.jpg

Any insight would be greatly appreciated!

2

Again:
Try it with some of the online regular expression checker (like regex101.com) and you will see why it don't work.
If you would tell us what your Perfomer tag contains before and after your regular expression, maybe we could help a little bit more.

3

Nevermind, it's most likely a Musicbee issue. The regex does what it supposed to do. The problem only occurs when the performer tag looks like this:

Charlie Watts (drums (drum set))

It's the double parentheses that's screwing it up.