Thanx for the great feedback. I posted an update yesterday but I
don't see it here. Two days ago, the problem went away. However,
yesterday the problem came back. So I checked every exterior bulb
visually, w/o removing them, and they all look completely normal. All
signaling, hazard blinking, brake lights, and parking filaments are
all working perfectly. I can clearly see each filament in the front
bulbs and they look separated and each functions on it's own and
normally. ( I understand that there is still a chance that a filament
is "moving around." ) The rear bulbs are not as easy to see.

Would it make more sense to pull the cluster or all the bulbs as the
next step?

Thanx!
John