You'll probably find the weld that holds the stub assembly to the rear axle, most probably on the RHS has broken and is causing it to rotate on the shaft and hence the left wheel sags. The left wheel sags because the height adjustment lever is holding the right wheel at the desired height. This is a common issue on the Honda's and a genuine new rear axle is about $140 last time i got on priced. You can easily weld it, just sit the mower on a bench and jig it up so all 4 wheels are flat and making contact on the bench top, remove the wheel and weld away. Have a wet rag wrapped around the back of the shaft so the heat does not melt the bush.
I've used your picture as a reference to what i'm talking about but it's normally the RHS that craps out on the Honda's i've come across.
