Often folks deem that the hard drive is problematic when the fault is that capacitors in the recorder's power supply are failing or have failed preventing the hard drive from spinning up. This is addressed here:
The linked post suggests sending a DMR-E85H to the Panasonic Service Center in Elk Grove Village Illinois. That Service Center no longer services older Panasonics. The Panasonic Service Center in Elgin Illinois currently services older models and hard drive equipped models. Current information is found here:
If your hard drive has actually become problematic I would suggest reformatting or replacement in order to restore full functionality to your DMR-E85H.
The Digital PCB is the "brain" that oversees every aspect of a Panasonic's operation. When the Digital PCB senses problems with specific component(s) or part(s) there is a disturbance to the general and specific functionality of the Panasonic. Sometimes the Digital PCB itself becomes problematic. Most often, these problems prevent using the recorder and its various features until there has been a repair/replacement of the problematic component(s) or part(s).
There are a few exceptions. In late June I purchased a used DMR-EZ47 VHS/DVD combo recorder that was advertised as having a non-functional VHS mechanism but with a fully-funcional DVD Drive. In that case the problem with the VHS mechanism did not prevent use of the DVD Drive. But what if I had removed the VHS mechanism? The Digital PCB would have found that the overall functional integrity had been compromised so that this Panasonic could no longer function as a DVD recorder.
I could have used this EZ47 as a DVD recorder the way it was. Since I have a DMR-ES35 "parts machine" on hand (where the VHS mechanisms are identical), I set out to repair or replace the problematic VHS mechanism. I found two problems with the VHS mechanism. First, there was a problem with the alignment of the VHS cradle assembly's videotape visor release finger that prevented the videotape cassette visor from opening to allow threading the videotape along the tape path and across the rotating head drum. This caused the VHS mechanism to jamb at the point of the casette's forward travel just before it is lowered onto the drive and take-up spindles. This jamb resulted in a forced eject. The second problem came from some misalignment of cradle parts resulting in a secondary jamb during the eject process. I removed and replaced two cradle parts/assemblies, the most likely cause of these problems. Those were the upper cross-over brace and the lower cradle assembly. The repair procedure is reported and illustrated at the AVS Forum in three posts, beginning here: