The first question to ask someone (or oneself) when a wheel is playing up is ‘When was it last oiled?’ If the answer is an embarrassed ‘Umm…’ the cure may be surprisingly quick.
If oil isn’t the solution, you need to diagnose the trouble. It can be hard to tell where the noise/stiffness/whatever is coming from. One possibility is to start from scratch – first take off the driveband and just treadle. Is the drive wheel running quiet, smooth and straight (get someone else to watch) and are the treadle, footman and crank behaving as they should?
If all is well so far, add the driveband, flyer and whorl but no bobbin yet (assuming it’s scotch tension – with double drive you’ll have to include the bobbin at this stage). If everything is still running smoothly, add a bobbin with a very long leader, feed it in as though spinning and see what happens.
This approach can sometimes isolate the problem. I hope ‘Spinning wheel ailments’ will provide a few solutions.