Screen goes blank only on sone channels

Screen goes blank only on channels 6.2 and 6.3 after a few seconds All other are fine. Says no signal but the diagnostic says 82% signal strength

crwdns2934089:0crwdne2934089:0 crwdns2934093:0crwdne2934093:0

crwdns2934109:0crwdne2934109:0

crwdns2889612:0crwdne2889612:0 0
crwdns2934285:0crwdne2934285:0