It sounds like the rotary encoder switch that's part of the mode dial isn't working correctly. The camera will need to be sent into Canon for repair.
-Demetrius
Bodies: EOS 40D & EOS 5D Mark IV
Lenses: EF Holy Trinity, EF 50mm F/1.8 STM, EF 70-210mm F/4 & EF 85mm F/1.8 USM
Speedlites: 420EX, 470EX-AI, 550EX & 600EX II-RT
