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.
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 🔥😉
What brand of tape?
First, check out the mechanical pieces on the deck and get that straight.If there is still an issue you should consider "baking" the tape.
Not an uncommon practice in the pro-audio world. Especially with tapes from the 70's.
One major tape manufacturer had a fleet of "rolling evens" visiting pro recording studios. It worked.

If I have to resort to 'baking' a tape to get it to work, it's time to discard that tape. The only stereo-related item(s) I have ever cooked are Vibrapods - when they get squashed from the weight of whatever they've been under, cooking them in a 200 degree oven for a few minutes will be like a dose of Viagra to them. How does that treatment benefit older tapes, tuzarupa? I've always stored my tapes upright in their plastic baggies and boxes to avoid problems with them settling unevenly. And I never used high-speed rewind except for very brief spaces because of my fear it would stretch the tape.
I visually inspected the heads/tape path with a hand mirror when I received it.
If the problem was buildup in the head gap, you might never see it.
If I have to resort to 'baking' a tape to get it to work, it's time to discard that tape.
I would be careful about that. Once a tape is baked, its useful for some months before baking is needed again. If baking it properly doesn't sort it out, **then** its time to discard it.

To avoid having to bake tapes I have two tips. First, place the tape in a plastic bag when it goes in its box. Place a small bag of Silica Gel in the bag with it. Second, never store tapes in the basement- if in long storage, place them in the attic, or other location that tends to get warm (and tends to be dry). I store tapes I'm working with on a radiator in my house. The heat helps keep moisture from attaching to the polymers of the tape.