Writes to derived tags do not trigger history entry on source tag

Starting with 7.9.12 I have been having issues with the source tag of a derived tag in a UDT not logging history when the derived tag is written to, any changes to the source tag are logged properly. The actual value of the source tag updates correctly in both Ignition and the PLC.

I have the source tag history set up to evaluate on change, the value mode is discrete, and the max time between records is 15 minutes. The forced history update at 15 minute intervals only records values that were done directly to the source tag or in the PLC (e.g. if the derived tag wrote a value of 65 10 minutes ago and the source tag had a value of 50 written a hour ago, the historian will log a value of 50 at the next 15 minute interval.

Prior to updating to 7.9.12 all changes to the derived tag were reflected in the historian. So far I haven’t found a way to correct this so I may have to either work around it using a tag update script or revert back to 7.9.10. Any suggestions for this would be helpful as I would rather not have to revert back to 7.9.10.