I am sure there are other good units out there besides the DD33, but I can only talk about the units I know.
Note: After I made the test and found the walkman guilty, I opened it up for the (hopefully) last time. I knew something with the head part was problematic. Since the ribbon wire of the head assembly wasn't making a good contact from the start it had lower volume when playing on reverse but when I touch the ribbon wire It would get fixed temporarily but I didn't removed it because I was scared of breaking the wire completely. But as a last struggle to fix the deleting issue I pulled it off from the socket. It was unusually dirty . I cleaned it with wd40 and It become nice and shiny. Then I put it back and did the same test with my 3 minute tape (after recording the deleted parts back). I played the same 3 minute tape for 1 hour. I checked the sound to see if anything got deleted but nope it was fine. Maybe the problem fixed when I cleaned the connection. Maybe 1 hour of test wasn't enough, what do you think ?
Sounds like the dirty contacts may have been the problem, hopefully it is and now you can enjoy your unit.
I hope you don't mind me chipping at this point, but I had a similar problem with an Aiwa TP-S101, The way the transport works is that there are a couple of permanent magnets either side of the head, (2 because the machine is capable of reverse recording!) anyway the magnets are placed on pivots. when not recording the magnets stay clear away from the tape, when recording is selected these heads move into position by way of the mechanism with an internal solenoid engaging the magnets when ever record is selected! Mine were stuck in the up position!!! I think it ruined my REM out of time album! There are others machines that use this same technique, Kenwood is another place where these permanent magnets can be found. Kind regards Warren
My REM Out Of Time album got destroyed too. I recorded it over yesterday. Its special since it has a bonus record at the end so I can fell your pain