Yes; the spring-loaded plunger in the trip assembly is a notorious culprit in the "won't unhook unless fired" syndrome. That along with the cocking slide return spring being damaged or crudded up beyond function.
Years ago, hand-loading for my 28 ga., I changed powders (was using 800X) to a coarser-grained powder and immediately noticed trouble from time to time opening he gun. Close examination showed individual grains of unburnt powder had blown back into the action around both the bolt trip release. Just those tiny obstructions were enough to bind up the action. Once I changed powders, the problem went away.
At the first Greenwich Fine Arms Show about 7 years ago, a man and his kids showed up with "Grandad's old duck gun", a well-worn 30" VH 12 ga. in the 105XXX SN range that would literally not do anything - open, cock, fire, etc. With the man's permission we removed the trigger guard and floorplate on a side table. When we took the floorplate up, it looked like someone had taken a huge dollop of wheel bearing grease, packed the action, then screeded the excess off with a straightedge. You literally could not see any of the internal parts! Whatever lubrication had been over-applied over the years, it had congealed and almost solidified in the action. We held the action over a trash barrel and blasted all the crud out with Gunscrubber, then a light pass with WD 40, wiped off, and lightly oiled it. Reassembled it and everything worked like a champ. The owner said he could not ever remember the gun having been disassembled and cleaned during its lifetime.
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