The hub that I set up for my neighbor has me completely frustrated and stumped. Don't know if it's the sunrise/sunset bug (with a negative offset), or something else like a corrupt database, but his simple lighting rules are not working correctly. He has only a handful of devices and rules so starting over may just be the easiest course of action. My question is: what's the best way to do that? Would just deleting and re-adding devices and rules be sufficient? Or would I need to do something more drastic like flash the whole hub (which I don't see a menu option for)?
If you're saving the backups external to HE you could restore from before anything was added. Of course that depends on how long the neighbor's HE has been in service and how many backups you store. I'm going out on a limb here because you haven't addressed either.
Another option is a soft reset via the diagnostics page on port 8081. DO NOT do a full reset!
I agree with @LosinIt :
You didn't tell us much in the way of basic info, such as: do the devices operate correctly from each device Info page? If yes, then "Starting Over" isn't such a good idea.
If the devices are Included correctly then "Starting Over" isn't such a good idea because there are still more 'Recovery Steps' available. Settings:Shutdown then when the red light comes on, remove power (at the wall, not the hub because of the delicate micro usb) and wait 60 seconds to allow the internal power to dissipate completely. The Z-Radios don't ever shut down otherwise.
The aforementioned Soft Reset can be a much simpler way to "Starting Over" as well. Usually a Soft Reset is coupled to a restore of a saved backup. Use this process precisely:
https://docs.hubitat.com/index.php?title=Soft_Reset
I think the best advice I can offer from the little you say is:
- Save a backup to your PC.
- Settings:Shutdown -> power cycle (at the wall)
- Restore the backup from your PC.
- Check all the devices individually from each Device Info page.
The goal is to get some clarity on where the problem begins. 
