Good question 
Previously when I went to Settings|System|Display, there was no 1080p option. Now (presumably thanks to your changes) there is - and selecting it expands the picture back to normal.
And when I reboot… it comes up correctly. I’m pretty certain it was at 60Hz before - he’s the latest post-reboot logs (run through grep -v -e /mnt/video/movies/… -e /mnt/video/short/… -e /mnt/music/…) for reference:
https://paste.osmc.tv/wonovoteso
Re disp_cap - curious. I log in via another account, then ran ‘sudo -iu osmc’, and then the commands you see. If I remove your ~/.kodi/userdata/disp_cap file, it fails - but whittling it down to just one line, 1080p60hz, everything works.
In case it’s of interest, here’s a syslog segment from a month ago, when it worked without disp_cap:
https://paste.osmc.tv/huyoweriyo
and here’s another from today, when it failed (with times removed for easier diffing)
https://paste.osmc.tv/xiqisajoku
And in case it’s of interest - here’s the same thing with your disp_cap file:
https://paste.osmc.tv/xaseyivipa
My only guess is that the monitor or AVR is for some reason sending different monitor (EDID?) info??
I’m curious what’s changed given I’ve not upgraded software for several weeks, but if the disp_cap file is required for my (kind of unusual, 1080p60hz only) system to work - so be it - and thank you very much!