New Notes cannot be added to existing record after upgrade-V 1612 (8.2.0.749)

Following an upgrade to CRM Version 1612 (8.2.0.749) on prem, our client can no longer add notes to records that are existing.  Multiple notes can be added to new records, but when the record is reopened, no notes can be added.  This is not occurring on all entities.  The entity that it's occurring on is a custom entity.  IT is not occurring on all custom entities.

We have tried deleting the notes pane and adding it to a new section on the form.  This custom entity is part of an ISV product (IPM), and as such, we cannot move away from the managed form.

Any ideas would be appreciated.