Just went back and had another go, managed to get all the way through this time. When I played the first time I viewed those switches as a half size red and blue switch next to each other on the ground (2 seperate ones) rather than one switch with 2 colours. Also, the movement of the doors as they move up could be a bit smoother as my eye is drawn to them quite a lot.
I like the idea of you not having enough characters so sometimes they have to perform double duty.