Are you saying the slow boot times started after migrating your HIP IPS custom signatures?
In ENS, all those would convert to User-defined Access Protection rules.
If so, does the slow boot still occur when only those converted AP rules are disabled?
Yes correctly, boot times increased from about 50 seconds to up to about 5-20 minutes or even cause a system deadlock alltogether.
If we disable the custom rules the issue no longer occur (just like with the McAfee default policy)