You're making a mistake.
The proper "fix" is to re-shell it as 2 new tapes. That's not super-duper difficult, merely tedious. If you want me to do it, send it here, PM me.
Confirm that it has no mold. Nothing unusual that you see.
I cringe when I see services offerings "MP4" (or AVI or MOV) without giving actual specifics. You have no idea what you're getting from them. Sadly, they may not even be sure what they're giving you! Yikes!
BTW, on their site, this is somewhat nonsense:
Problems That Cannot Be Addressed with Physical Repairs:
- Lines that appear on the screen for the length of the film or sound problems
- The picture scrolls vertically or there is static on the screen
- Digitization interference in miniDV and miniDV HD footage
Each of those has multiple causes, and several possible fixes. So if they get that wrong...