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Do you have no eye cup on the camera? Try the minimal eye cup. I may have moved one from an older camera of mine or one may have come with my cameras, so I don't know what comes these days but, judging from pictures, it does come with one. Did it get lost or removed?
I find that my eye cups prevents accidental diopter change on my DSLRs.
If you have one in place, then I don't know how you could be moving the camera such as to change the diopter frequently, or even occasionally. Try a bigger eye cup.
"canon eyecup at B&H"