As discussed here: https://forums.beamdog.com/discussion/77629/version-1-79-issues-and-troubleshoot in NWN:EE recent-ish updates changed the way some files were organized to no longer be hard-coded. The original EMS.hak file apparently relied on this hard-coding for the Pale Master's AC bonus (among possible other things?).

Until the EMS.hak file included in the current version of Aielund Saga's workshop content can be updated to fix this, a possible work-around is to bypass it entirely with "EMS_FAKE.hak" (downloadable here: https://neverwintervault.org/project/nwn1/hakpak/ems-enhanced-magic-system). Simply download the "Older Version" grab the file and rename it then overwie the workshop content version of the file and it should be fixed... though obviously this comes at the cost of removing all changes to the magic system that were originally in place.