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 5D Mark IV
Lenses: EF Trinity, EF 85mm F/1.8 USM
Retired Gear: EOS 40D, EF 50mm F/1.8 STM & EF 70-210mm F/4
Speedlites: 420EX, 470EX-AI, 550EX & 600EX II-RT
