I have two HD box tops, they will reboot randomly, this can take up to 30 minutes before programming returns and can happen several times a week for each of the two box tops. I have called several times asking for assistance and now am at the point of frustration, that I am reviewing other provider options.
Have you checked your router to see if it has rebooted? Could cause the STB to reboot if signal is lost for long enough time. Also STBs have good uninterrupted power right? Any momentary power loss results in a reboot. Just for fun, reboot router and see if problem continues. Also check coax connections from ONT to splitters and from splitters. When the boxes were installed did they replace splitters and coax?
What model stbs do you have?
If they are older, it is possible they are starting to fail.
Delay in guide could be router issue as noted. Try rebooting router.
Also, check coax connections. Start at ont and verify that all connections are tight.