Hi,
I have the same problem. Had it before (indeed condensation issue). There is no other remidie than dry the tape loader OR bring it to service. Currently, I have the same problem but not due to condensation, but dirt in the tape carrier (have been filming in the desert). So will have to go to service again. With previous cameras also never had this problem, it seems a weakness/flaw in the design of this Canon camera. Try to make use of your warranty.
Good luck!
Gr. Erik