Where to add oil on my Generac Guardian RV 6500? Pic inside

I bought a used 07 Georgetown Class A that came with a Generac RV Guardian 6500 (Wish it would have had an Onan). So I have had the generator just shut down on me a few times and thought maybe it was a low oil pressure warning or something. Usually will start right back up after shutting down and run for a few more hours before shutting down again. This is with basically no load besides lights and TV's going no A/C or microwave etc.

So I checked the oil and am a little confused. There appears to be 2 oil fill spots on this generator... Photo here.



The lower yellow plug has a dip stick and the upper yellow plug has no dipstick but both yellow plugs say oil fill. So I went through the 16 minute Guardian maintenance DVD and of course they say nothing about the Extra Yellow plug at top and don't even refer to the lower one. Instead the show an entirely different generator when showing how to perform maintenance.. So I break out the owners manual and it shows the Upper yellow plug in the photo of the parts but doesn't show it called anything. The lower one shows it's the Oil Dipstick and fill tube. So what is this upper yellow plug that says Oil Fill? When I take the cap off it looks dry inside. Did the previous owner just put an oil fill plug on whatever this thing is? I don't want to put oil in somewhere it shouldn't go. Any opinions would be appreciated. Thanks..