I'm having trouble getting my right side wheels to move. They've been a bit touchy for years, but I little rock forward or back has always done the trick. Now the right side seems to be locked for the most part. If I put the parking brake on and then release it I can usually get about a metre or less of movement before it locks up again. When the machine moves, I can hear a "ka-thump, ka-thump" sound each time the wheel goes around, and it looks like the parking brake link jiggles in time with the "ka-thump". I'm thinking its either a bent locking pin for the park brake or a chain problem. Please help me ID the noise. https://youtu.be/zQ-9MMqRCt8 Many thanks!