When I had problems with a faulty brake light switch, as well as the VDC & ABS failure warnings I had a couple of occasions when the cruise control also stopped working.
Diagnosing the fault is tricky, as a faulty brake light switch doesn't set a fault code & the brake lights will be working normally.
The switch has two pairs of contacts. If you open it up you'll no doubt see that one pair is heavily burnt, which will increase the resistance across them to the point where they intermittently appear to the ECU not to be closed when they are - this gives two conflicting signals resulting in the problems you're seeing.
Where are we going & why am I in this handcart?