ONAN generator makes clicking when running?

First post but been reading post here for a long time now, great knowledge on the site.

I was exercising the generator while installing vent covers on the roof. Kids were in the camper with the AC and radio on. While on the roof I started hearing a clicking from the generator. It seemed like it was sporadic, click several times in a row and then stop for a bit. Then it would do it again but only a couple times then stop. When I looked at the generator I didn't see anything sparking or odd.

Has anyone seen this before?

Thanks