Well, I tried changing the callouts plugin, but it seems to happen with any and all callout packs to be honest. JM Callouts Remastered, Tacsims casual callouts, supercallouts, 686 callouts, and others all seem to crash the LSPD:FR plugin after detaining a ped spawned by those callouts.
I will try to find a different set of callouts, one that finally might not crash LSPD:FR, but otherwise I'm left completely without any callouts at all.