Im also seeing similar - huge drop in frames just at EGKK. Tested on YBBN, OTHH, EGLL - all MS24 Premium products and getting 100+ with the Fenix, but at EGKK 5-20FG. I'm pretty sure it was fine a few months ago at launch.
Update: Uninstalling, opening MS24 at EGKK, then reinstalling EGKK, seems to fix the issue.