With a quick check in the manual Grumpy shared I found the following on page 12
1. Push and hold the switch at START until the genset starts. The status indicator light on the switch flashes while cranking
. It will come on solid when the starter disconnects...
So, what you saw reads as exactly what you should see while cranking, a flashing switch. I never noticed that on my Onan 4000, likely because my big hand is always in the way to see the switch. I will look more carefully next time I start mine which I may do later today. ~CA