No. It's not normal.
Liquid filled boost gauge? I don't know of any, but I haven't seen it all. A boost gauge buffer???????? What in the world is that? Who uses them????
I have never, in all my many years of working of diesels, seen a boost gauge flutter.
There is a fellow from Northern Ohio that found his head gasket blown when his gauge began to flutter, when all the time prior, it did not.
Sorry to be the bearer of bad news, but it's not supposed to flutter. I personally have never seen that, but I cannot say which ones are/were Autometer units. I don't use them myself, in my trucks, and don't personally know anyone who does.
My boost gauges (in my trucks) are steady like a rock and same in the vehicles (Dodge Ram) trucks I drive time to time.
To repeat the above....it sounds a little wierd to me .....too!