While Teacs overall are reliable decks, and a similar 6 button transport was used many consumer and semi pro models that was bulletproof, they have a number of common problems outside of those listed at the beginning of this article.
Seized pinch roller bearing. This is super common on all Teac A series, due to sticky white lithium grease used at the time of assembly. This grease hardens over time, and seizes up the sleeve bearing that the pinch roller moves on. I have an article in the tech section of this site how to fix that. On occasion, the tape lifter sleeve bearings also seize up, those need to be cleaned and lubricated as well.
Noisy transistors. Some early Teac models (A-3340 comes to mind) in the early 1970s used round silicon transistors that are known to go intermittent, and should be changed out with standard NPN low noise transistors (I use KSC1845). Later models stopped using those transistors, and are fine.
Cracked PC boards- specific only to the A-2340S and the A-3340 series, the switches on the head block stick out the furthest from the deck, and the PC board behind them tends to crack if the deck is hit on those switches. Replacement of the PC board is difficult, as many used ones are cracked also, and the amount of wires going to that small board are insane, however usually the PC board is cracked around the mounting screws only, and can be repaired rather than replaced. Still, it’s finicky work.