I only have this problem when a large clump is newly transplanted and I need to stake it for a couple of months until it locks-in to the ground. Otherwise the wind knocks it over. I don't know what the longterm solution is for you, but you can stake it now to prevent further damage. Ultimately, the only thing that may work for your location is to divide out the clumps that are having problems and re-locate them.

When large bamboo grows up to the edge of a pond, some of the culms nearest the water (where it is very soggy) seem to naturally tip and fall towards the pond over a period of time. You don't say how large your bamboo is, but one thing you might try is to top some of the culms on the low side of the slope. That will greatly reduce the forces of gravity and the wind, and that might be enough to stabilize the rest of the culms.

What type of bamboo? clumper, or runner? And how tall is it? What kind of soil is it in?