Actually Im not sure why this is happening, we already fixed this to solve the AC/DC issue.
If you go to Preferences:FileName Masks, select your mask and Edit, then modify data in Example 1 so it looks a bit like your album do you see the issue or only when run it? Because for my mask it converts any / in fieldname to - and this is done automatically by SongKong I havent coded it in the rename mask itself.
And I tried it for real on an ACDC folder so although the Album Artist is set to AC/DC the folder name is AC-DC

This is on Windows 10, but the conversion is made in the code so I dont think this is actually a Windows 11 issue.