Unfortunately, you missed the part in the manual and in other posts about flattening the flange on the fuel tank where those plastic bumpers on the frame contact the fuel tank. Those need to be against the flat of the tank flange. Not against the edge like showing in your picture. You need to correct that to get a much more solid fuel tank mounting. The provided bolts are a bit short and many replace them as you did. But leaving the flange bent like that made the situation worse.