Hardly a "bug", but the "PVWatts" page in the Help docs has a section entitled "Differences between PVWatts Version 5 and Version 7" with this sentence:

Account for incident angle reflection losses in the module cover using the physical model for incident angle modifier to account for reflection losses of both direct and beam irradiance.`

"both direct and beam irradiance" is of course redundant; I assume this should say "both direct and diffuse irradiance" or similar.

Here is the relevant area of the rendered HTML:

https://github.com/NREL/SAM/blob/702754d8f837fcaf7dd6a50155a5c1a013a87be2/deploy/runtime/help/html/pvwatts.htm#L90-L92