Yes, it seems like it's a bug on the handling on slashes on the RMC tool on the Mac. The workaround is to add the code to a new calculated field instead of putting it directly on the rename tool.
Additionally, it sounds like you have albums with different [Date] on its tracks, and that may cause the previous expression to fail in some cases because it was grouping files by Year as well. Try this:
1. Create a calculated field called "Album Artist - Album" with expression:
[Album Artist (Auto)] - [Album]
2. Create a calculated field called "Album (renamed)" with expression:
save(FieldQuery(Album Artist - Album,[Album Artist - Album],Catalog #,1,0),_catlist)/
save(if(isempty([_catlist]),/(replace([_catlist],;,/,/ )/),), _catalog)/
save(trim(replace(replace(replace([Album],[Lossy],),[Incomplete],),//,_)),_album)/
save(FieldQuery(Album Artist - Album,[Album Artist - Album],Date /(Year/),1,0),_dates)/
save(ifcase(listcount([_dates]),6,2,/[listmath([_dates],0)-listmath([_dates],1)/],1,/[[_dates]/],0,,),_years)/
trim([_years] [_album] [_catalog])
3. On the rename tool, use this expression:
[Album Artist (auto)]//[Album (renamed)]
You can add columns for "Album Artist - Album" and "Album (renamed)" to your view to see if they're OK.