The tiller shaft is tapered and they can grow on. You can remove the long bolts and spray PB or WD in there. Let it soak overnight then use a long punch or pipe and a hammer and it it from the back side. They will or should pop off
Another challenge is removing the wheels if they haven’t been removed. The first one I had I drove the roll pins out and had to heat the inner part of the wheel with a torch. I used a pipe wrench and tried to rotate the wheel to break it loose. It’s a good idea to remove the wheels once a year and clean and lube the axle shafts. If they get stuck it’s a pain if you need to replace or repair a tire