What Knott said +1.

It's easy to get into a pattern on the trainer and not move around much. You could be rotating in a little and staying there too long or any number of things. Plus, the trainer requires more muscular effort per 1 hour riding than road riding does so you may be over recruiting your calf muscles.

Try changing it up, do 5 min at 90 rpm med effort, 5 min low effort 100 plus RPM ... Try to change something every 5 min or so. That may take care of it.

Going to 0 deg of float can be hard on the knees but it does not affect your ability to unclip.