I've set up my Ensoniq SD1 to see whether I can reproduce your problem there, but nothing doing.

So I've downloaded the TS12 manual and looked for Glide and Portamento, and all the settings I can see are specific to voice or sample settings, nothing global at all, so that's no good either.

The keyboard isn't stuck in a voice edit with Glide set to Mono or MiniMode is it? Although I'd have thought that would get reset if you powered off.

Could all the voices have their Glide control set to "Pedal" - if you plug in the sustain pedal does it work like you'd expect or is it turning glide on and off?

After that I fear it is reset time. You can save the settings and voices to floppy or sys-ex can't you - although if this glide issue is some hidden system value it might just come straight back again!

Best of Luck

John