Picking up on this thread because I have the same System Problem messages, thanks in advance and sorry for long post. 2018 Touring 2.0T with 54k miles. Yesterday morning driving down the Highway using ACC, cruise stopped working and got this message 'Some Driver Assist Systems Cannot Operate: Radar Obstructed'. I pulled over a few miles down the road and sure enough the plastic Honda Sensing cover was not clipped onto the Radar unit. I didn't hear or feel anything but obviously something hit it hard enough to knock the cover loose, I doubt it just worked its way off over time. The Rader itself looked fine, intact, solid, so I just clipped the cover back on and all was well. Continued on with the day of 100+ miles highway driving with everything normal and using ACC. Then late afternoon the ACC stopped working again, this time I have three messages. 'ACC Adaptive Cruise Control System Problem', 'CMBS Collision Mitigation Braking System Problem', 'RDMS Road Departure Mitigation System Problem' all followed by See Your Dealer. Plus the BRAKE SYSTEM light is on under the speedometer. I took pics of all of the errors as they came on.
I spent some time searching here and elsewhere to rule some things out. I checked the brake fluid, it's clean and full. I checked the battery (15 months old) and with car off it is at 12.8V @ 820 CCA when load tested (good/pass). I pulled the battery terminals for 10 minutes and then reconnected. No check engine light, no codes to read from auto shop guy. The three System Problem scroll in the MID and BRAKE SYSTEM light stays on. They don't go away on a restart, they didn't clear with a (battery) reset, and ACC for sure doesn't work.
I have NOT checked the brake switch (assuming in footwell/dash area behind the brake pedal?), that I've read some have had the dealer replace. It's awkward down there and can be a back spasm creator but hey, I'll check it out if I know what I'm looking for. I'm out of warranty, of course, looking for some ideas before I make an appointment at local Honda dealer for their diagnosis. Besides the three things that don't work, the car drives fine and normal, no other symptoms.