Hi everyone. I was cutting long grass but suddenly felt the mower driving speed dropped rapidly, the self propelled part seems to having trouble.I lifted up rear wheels and engaged self propell cable and both wheels spin, but as soon as I put wheels on lawns, it does not drive mower forward, I had to push mower to finish off rest of mowing.

Anyone familiar with this kind of problem for this Victa 550 single speed drive?

Thanks