Did Nixon Erase My Tape?

During my Army days in the early 70s, I bought stereo pieces while I was overseas and had them sent home to wait for me when I got out. One of the pieces was a Teac RTR, and over the next 12-15 years, I made around 50 7" tape mixes, all of them at 7 1/2 IPS. I still have those tapes and have acquired three nice RTRs.....a Teac A-4300SX, a Teac X-1000R, and an Akai GX-636. I was playing a tape today on the X-1000 and when I hit 'reverse' to play the second side, all I got was silence, with an occasional garbled sound every 5 seconds or so. At first, I thought maybe I had erased the second side and never re-recorded back over it, but the back of the box (where you would write in whatever you recorded) showed no changes.So I removed the tape from the right take-up reel, flipped it over so that the B side was now the A side and re-threaded the tape back on the left reel. The recording played beautifully, with no problems, and I'm trying to figure out where the problem lies. The tape was originally recorded on a Teac A-4010SL and I think this is the first time I've played it in at least 20 years. I'm thinking that tracks 2 and 4 just don't line up correctly with the reverse-playback heads on the X-1000, which itself seems goofy to me. Any veteran tape-heads out there that have an opinion, please let me know. The X-1000R has bi-directional recording capability, which the A-4010SL did not.
Thanks for the suggestions atmasphere, oldhvymec, et al. The problem evidently rests in the pinch roller/capstan domain as a different tape was played with thew same result. Dirty tape path isn't the explanation....I've only used the deck 2 or 3 times since buying it over a year ago and I visually inspected the heads/tape path with a hand mirror when I received it. I guess any device with as many moving and inter-related parts can be expected to require more and more maintenance as time goes on. But I'm in love with the sound from RTRs, so I'll just have to suck it up.


Talks of "Non Pinch Roller Parallelism", In other words it works one direction but not so well in the other.. Bi directional playback is really cool, but it also adds a complexity to simple playback. The head bias and adjustment are more complex. Still no biggie.

I’ve never tried it...BUT BRAVE on good fellow brave on. I’ve always had Studer and Otari though as a kid I had a Military Roberts 770 close to  Teac adjustment

Thanks for the service manual data-base info oldhvymec. It will help me to delve into this problem and decide whether to tackle it on my own or get competent help (I'm leaning toward the latter). I learned the Law of Diminishing Returns in painful way years ago when I replaced a trap under the kitchen sink, but failed to seal it correctly. Woke up the next morning to an inch of water on the flooring. Or maybe that was Murphy's Law?
Every time one of these threads come up, with one or more persons singing the praise of R2R, I am tempted to get into it.  Then, one of my local friends who is already deeply into it says, no.  That I would be crazy.  But when I listen to his tapes at his house, the sound is very very good. He's invested many thousands.
R2r is the best legacy playback and recording format. It also happens to be the most limited in regards to pre-recorded releases available.
If you are into making your own tape recordings, then R2R is the best. Hifi VHS is also very good and a much easier format to deal with but not nearly as sexy or applicable for live recording 🔥😉