I've a dim memory of this happening to me on 2 x 20 2.4GHz and found somewhere it was only using the second channel when carrying traffic. Not when idling. Which I then proved for myself. I didn't have any kit that could use 5GHz at that time.
My broadband basic info/help site - www.robertos.me.uk.
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Connection - AAISP Home::1 80/20. 200GB. Sync 70745/12295Kbps @ 600m. BQMs - IPv4
Edited by RobertoS (Sun 02-Sep-18 22:21:19)