A long shot but, not all adjuster screws are the same length.

Has one been replaced and it’s just longer than the others?

On another subject...... if you’re running the P2806077 spring...... that might be my most disliked spring of all time.
Not enough on the seat, too much over the nose, and nowhere near enough travel to run the higher lift cams it’s recommended for.
I actually refuse to install them on customers heads when they send/bring them with their heads.
In fact, if someone called to order I cam from me, and told me they were going to run those springs........ I’d pass on the cam sale.
I’m sure much of the trouble MP head with the failing .620 cams was the result of people using those springs.

It’s a pretty high rate spring........ too high for any type of regular hyd cam and lifters imo.
I’m sure it’s giving those lifters a serious workout.

As to the question posed in the thread title......
The only time I’ve ever seen the plunger “stuck” in any position on a hyd lifter is if it’s basically seized in place.
Could this happen with the plunger at or near the top of its travel?
I don’t see why not.

Should be easy enough to determine, especially with those big springs.
Turn the motor over until that valve is fully open........ and leave it like that for a while(an hour, overnight, etc).
After a period of time, turn the motor over until the valve is fully closed...... then go just a bit further to ensure you’re on the base circle.
At the point, the spring load should have pushed some of the oil out of the lifter, and made it “soft”. So you should be able to grab the rocker arm and see if you can compress the lifter any.
If it’s still 100% rock hard with zero “give”....... it probably needs more scrutiny.

The “normal” scenario with hyd lifters these days is....... you rotate the motor to get the valve fully opened......... and you can just watch the spring load collapse the lifter.