There is no IntermediateFilePath designated for the operation, but it should probably be the work folder for the operation.  So it's been using a Temp folder for these files all along.  The file was created while HC was on the secondary node, but is now back on the primary and that path does not exist.

We resolved this by:

1) Create  /intersystems/HCENG01B12/mgr/Temp/ temporarily on the primary node

2) copy the iostream file to that folder

3) run the rollover so the file gets processed and the operation "forgets" about that file

4) disable the operation

5) delete /intersystems/HCENG01B12/mgr/Temp/ from the primary node

6) update the operation's IntermediateFilePath to the work folder

7) return the RolloverSchedule back to T23:30:00

8) restart the operation