Radar not available

Hello all, newbie here with my 2nd Taco. I have a 2018 fleet Tacoma 4wd 16K miles. Recently in clear dry weather doing 75 on expressway with cruise on when yellow dash warning light came on and in dash stated radar unavailable and brakes applied hard. Shut off cruise but warning stayed on 10 min. Happened a few more times in a week. Now when it happens dash states clean windshield with or without cruise on. Dealer wanted $600 to "calibrate" with no guarantee of a fix. It is still under warrantee so I got Toyota involved. Dealer is not getting and codes sent from computer and dealer has seen the warning light come on. Now they say $240 to calibrate with still no guaranteed fix. Toyota getting involved again as I refuse to pay for a safety issue under warrantee. I have seen other posts about a leak in the senser seal but this happens when dry. Anyone have similar problems? Thanks.

 

Another note, I pulled off to side of road once when this happened, put in park, shut off engine and restarted warning gone.

 

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