Cruise control vibe 2003

2003 Pontiac Vibe, 5 speed manual, 70K miles
Recently the cruise control started shutting itself off; if I keep turning it on/off it will hold speed again for awhile, but a few mins later the same problem reappears. Some days the CC works just fine; other days it flickers on/off. The cruise light starts flickering too when this happens, but doesn’t remain off.
I am not touching the clutch, brake, gas.
Seems unrelated to weather or road conditions.

A similar (virtually identical) problem was mentioned in an earlier (2014) discussion by flea741, but that discussion is now closed. I am curious whether flea741 ever figured out the problem, or if anyone has any ideas.

Are there any other warning lights lit up when the CC light starts to flicker?
If the Check Engine Light, or the traction control light, or the vehicle stability control light, or–possibly–even the ABS light is also lit up, that would be a clue to the source of the problem.

No, there are no other lights that go on or flicker when the CC lights flicker.
By the way, sometimes the CC stops working (turns off) without flickering of the CC lights, at
other times the lights do flicker. So there no one-to-one correspondence.

The brake or clutch switch are probably out of adjustment.