Please be warned first of all: settings changed while the camera is set in C1 or in C2 Modes, will not be remembered by the camera, though they will 'stick' in the real modes, such as P, Av, or M, etc.
Then, after that, if that is not the problem, the camera may have an internal 'coin,' or smaller, battery and it may have gone bad, making the camera lose some settings changes that it should have retained. This implies, if so, that the camera needs servicing to replace that internal battery, and/or to fix some broken internal connection from it to the rest of the camera.
How old is the camera, please? in months or years since you bought it.
Has the camera been dropped or otherwise subjected to mechanical shock(s) in its lifetime?
Has the camera been operated in or subjected to, temperatures below 32 degrees F (freezing point) or above about 100 degrees F ?
Has it ever been subjected to a humidity higher than 85 % or gotten wet ?
Has the camera been operated in a gritty or sandy environment, such as a beach, a seaside, a construction site, or the like?