Hi, for a number of reasons we recently switched Forest Pack's instancing method to use the same technique as V-Ray Instancer. This seems to have affected some of the Cryptomatte functionality. I'll pass it on to the development team, but since V-Ray Instancer is affected in the same way, it's likely to be something that Chaos will need to look at.
As for IPR mode, it's always been my understanding that generating crypto masks only works with bucket rendering. Unless this changed in recent versions.