since all I tried did not fix it, I rebooted the VM my HA is running in, that finally fixed the issue.
If no further posts follow, this fixed it permanently and it was a one time glitch (probably related to HA updates as I think the issue started with an combined update from core and supervisor), but I got a feeling in my gut that this is not the case, so watch out for further diagnostics.
funny thing is, all other mqtt commands where executed normally. only the tablets stopped responding to any mttq command sent, not just the speak via tts commands, they kept transmitting their status via mqtt how ever.
I also upgraded this morning, before I tried the reboot with the host, I think it was the supervisor to 22.3.5 but the restarts required with that update did not fix the tablet thing.