HRX 217 wheels locked when pulled backwards

Rear wheels lock when pulling mower backwards except when engine runs. I've taken wheels off and checked, cleaned and lubed the ratcheting drive gear making sure it was put back together properly. I put a vise grip on the axle and got it to turn a bit, just a little bit. (It kind of gave and then stopped, I didn't force it anymore.)

I was thinking it might be the axle shaft is stuck to the bushing but that doesn't explain why I can get it to roll backwards when the engine is on.

Anybody have thoughts on this?

Thanks

I have a Honda mower that does that, too.  I saw a few videos on You Tube where guys show how they fixed the problem.  Apparently, so models have a plastic sleeve that slides over the shaft.  It gets almost bonded to the shaft. 
Mine has a steel sleeve, but it still does it.  The other thing is the adjustment on the belt drive cable. 
I have not completed my repair yet, since i just started it today.