My antenna channels disappear after going into a different app (and when you turn off the TV). Following RokuDanny's advice, I obtained the following incident information, after the most recent occurance:
Roku device model: 7209X Roku TV
Serial number: YN00X9417097
Device ID: 9Y600X417097
Software/OS version: 11.5.0 build 4312-38
Tracker ID: 97-187-473