not sure what you mean? the black plastic wheels not turning? or shaft holding the wheels to adjust up and down at preset height?
If you meant thee shaft, its a difficult decision. normally if I didnt have paint to worry about I would add heat from torch on outside collar of shaft till its hot enough to melt candle wax. Let it cool, support bottom of deck and give it a good whack on shaft downwards.
Otherwise, I just might add rust buster fluids you have in your garage. ( wd40 is pretty weak, you need industrail strength. I would mix up ATF and diesel 50/50 and coat the shaft and let it sit overnight before cleaning away with rust breaking fluid and try to free it.