Clutch pedal feels fine, but disk stays engaged, sometim

Hi everyone. Ford 641 gas, four speed, single stage clutch. In the fall I started noticing that the tractor wanted to keep going a little bit when I'd clutch and stop. Not much, just a little drag in the clutch, so that I'd have to use the brakes to stop it. Then after a week or two of that, in the middle of working, not after sitting, I've got no clutch control at all. The pedal feels normal and has full range, all external linkage in good shape, no noises heard etc, but the clutch was locked up. Stalled it out, but still locked up. Tested it out for a bit, still locked up, then parked it. Took off the loader a few days later, started to carefully back up out of the loader frame at idle engine speed, assuming I still had no clutch, pressed the clutch once by instinct, full working clutch no problem. Parked it under cover all winter, went to work on it today, still perfect clutch, no problem. Drove it around, warmed it up, clutching, in and out of reverse, no problem, no drag, perfect clutch.

If the disk had been rusted to the flywheel last fall, it wouldn't have started sticking in the middle of work, it would've been stuck from parked.

Anyone have any thoughts? I hate to split the tractor only to find all is well. But I hate to put the loader back on only to have to take it off soon if the clutch acts up again.

Thanks, Alex