Hi, nice box! hope you’ve managed to sort but if not - I’ve done a couple of Hitachi boxes recently a TRK 8200 and 8600 and found both had sticky mechanisms due to the lube going off and solidifying gic8 g similar problems to yours. Grab some cotton buds and some plastic and rubber safe cleaning fluid such as made by Nagaoka off the ’net and swab away all the old lube. I use a micro tipped mini bottle oil applicator (plastic safe oil) from Eileens Emporium to relube spinning parts on shafts (pulleys and gears) and lithium based grease for the sliding parts (usually metal or plastic) found in the mechanism - a cocktail stick is perfect for this. Banging some music on whilst your doing this job really helps popping out the capstan (the steel shaft about 2mm in diameter fitted into the usually grey metal flywheel about 40mm diameter and, watch out for the very small spacing washer and lock washer on the shaft), cleaning the capstan shaft and bearing mounted in the cassette mechanism back plate will make a massive difference - you’ll know you’ve got this right as the capstand will spin for ages without its drive belt fitted. All the best and enjoy the problem solving, sadly there aren’t any manuals for repairing 40+ year old boxes bit hope you enjoy writing your own story.