Thetford c2 cassette toilet leak

Water leaking from flushing tank which is on the right of the toilet, pump is working okay and waste tank housing is dry so don't think its a faulty seal.

There must be a tube from pump to flush knob does anybody know how to get at it. Floor of toilet very wet, no smell so I assume it is flush water.

Knob to flush is very stiff to turn as well but on waste tank the knob opens it easily.

Can anybody help thanks.