I have had this same problem happen to me as of yesterday. Heard brief crunch noise while traveling straight. Shortly after, no movement from left side. Up and down, and right all work fine. If I were to open the oval plates covering the sprocket housing(not sure if that is correct terminology). and can see the large front sprocket, there should be a chain over the top of that sprocket right...? I can hear spinning when left forward and reverse is enguaged, but no grinding, and cannot see movement. Is it possible that that the chain fell off due to loose tension. How can I check to see if chain is broken or just came off? New to repirs on this machine ..Any help is a gift. Thans pjIt could be a few things, broken drive chain, damaged chain, bad drive motor, pump issue.
Can you swap drive motors from side to side and see if the problem moves?