Ive had luck with similar logic controlled tape decks by cleaning the optical wheel that drives the tape counter , usually its a little plastic gear wheel with reflective foil and alternately dark bands on it , theres a light source and optical pickup of some kind , Very often a coating of dust on the reflector prevents the machine from sensing movement of the tape ,it drops into play momentairily , but because movement isnt dectected on the supply reel side ,she just shuts down automatically .
Usually its possible to clean it without stripping the mech down , I just used a dry cotton bud against the wheel and turned one of the spindles until it was it was clean and shiney and working perfectly again.
If its one of the direct drive mechanisms your fortuneate as you dont have to worry about drive belts , theres also the tape type sensor switches up top ,but often theres one of these tiny leaf contact switches which senses the presence of a tape also , sometimes these can become misaligned ,damaged or the plastic actuator tip gets broken or falls off .
Theres a couple of tape mechanism gurus on youtube , very often parts were shared between several makes and models of tape , these guys have the low down on the faults that are prevalent with various mechanisims , and show detailed videos of rebuilding .
Sometimes grease dries up in the mech somewhere and prevents proper opperation of a cog or wheel , Ive had luck with the help of youtube tutorials in locating the exact mech rebuild video , then instead of tearing the whole thing appart I simply applied a small amount of silicon oil to the affected bearing surface . I used the spray type silicone oil , but I put a few sprays into a bottle top first and waited for any solvents to evaporate ,then used a hollow plastic tube ,like found in a cotton bud or biro, to pipette a drop right where I wanted it .
My guess is clean the tape counter sensor and you'll most likely be enjoying sound again . Best of luck with it .
* Autostop on the older machines was mechanically controlled , the newer ones with digital tape sensor and graphic display relies on a signal from the optical sensor, if that signal is not getting through your machine autostops itself from any mode ,FF,RW.PL