It should look like it's crumbling or puffing up. There mite be a sulfur or ammonia like smell with some types of gunpowders when they degrade. The only other thing I can think of is that there was a high amount of humidity present when the ammo was loaded and possibly the steel cartridge cases are corroding internally and compressing the gunpowder which in turn is pushing the bullet out. Also. The cartridges mite had been loaded with a type of gunpowder that bulked so much as to be highly compressed when the bullet was inserted into the cartridge case and and an insufficient crimp was applied and over time has pushed the bullet out or possibly in conjunction with with an insufficient cartridge case neck tension/grip on the bullet. You need to pull a bullet from a cartridge case with a collet type of bullet pullet, NOT a kinetic type bullet puller. If the gunpowder is indeed degraded, the shock from a kinetic type bullet puller could possibly set off the gunpowder of which one of the components of double base nitrocellulose gunpowders is nitroglycerin, which is highly shock sensitive.
Many moons ago I had a Remington 700 with 24" barrel chambered in 220 Swift that with 50 grain bullets was only producing low 3,700 FPS for muzzle velocity loaded with IMR 4064. So I decided to push the load by adding more gunpowder which in the final load testing, the gunpowder was filled the cartridge case to top of the case mouth. I used a brass dowel ram the screwed into the bullet seating die to compress the the gunpowder so I could then seat the bullet so as to not crush the bullet when seating it. I loaded this ammo up two or three nights before firing it and by the time was sblecto go to the gun range, the gunpowder had pushed the bullets out by about .150". I tell this because this has been my experience with bullets being push out after loading.