I take it the compresion test was done, cranking the engine.
Then the rings should seal and valves must be closing correctly.
If I remember right, the valves are supposed to turn to keep the seats cleaner.
It seems strange, but there is always an explanation for such behavior. Perhaps the compression test should last much longer for Cyl. 1? If the pressure is still correct, then there is something going on with the combustion. Are you sure the Spark Plug isn't losing pressure?
I'd just throw in another new plug on 1 and see.
Now, the pressure is highest when the piston hits the upper dead point. This doesn't mean that the there couldn't be a leak on the Head Gasket (just a thought) then again it seems far fetched, since the pressure is good.
Perhaps a weak spark?
Did it run before the new stuff?

__________________
Mostly, I don't know notin, I just know where to look.
I am looking back, to over 30 years in Electronics Design.
Electrons don't care if they move in a car, computer or relay!

95 W124 E320 M104.992 - Because, I love to repair, naaaah!
Over 221,000 Miles
Cheers,
Norbert