Reads like the ignition coil is failing due to heat. Not too tough to remove & replace. There are three resistance checks you can do with a multi-meter when the mower is NOT making spark. It could be the coil itself (2 measure points) or may just be the spark plug cap alone (1 measure point). A new coil is about $75 list price, and I'd probably go ahead and replace the cap too at that point. Tip: When measuring coil values, be sure the throttle lever is not in the STOP position.
You need to remove the fan cover / fuel tank to access the coil, but it does not need to be removed to do the testing. If you replace the coil be sure to correctly set the air gap where it mounts near the surface of the flywheel. A paper, factory shop manual ($35) has all the details, measure points/values, and is fully illustrated. Honda sells them direct on eBay and Amazon (free shipping):
Honda Power Equipment Shop Manuals on eBay
Honda Power Equipment Shop Manuals on Amazon
With the mower's FRAME (deck) serial number [MXXX-1234567] you can look-up parts at Honda's official parts look-up, or there are many Honda dealers online with similar catalogs. For mowers, you need the FRAME serial number, not the ENGINE number to correctly look-up parts.
Google any part number to find a Honda Dealer selling it online, or use this link to find a Honda Dealer in your area:
Find A Honda Dealer
Honda Factory Parts Look-up Site:
Honda Power Equipment, Engines and Marine Factory Parts Lookup
Sample online Honda dealer with extensive parts listings:
[url]www.boats.net[/URL]
FYI, there is no low oil sensor on the HRB215 mower.