Also check to see if the bolt release tab is binding in the bolt stop groove. Slightly bending the tab can do wonders if it's binding.
Sitka is right about stuff like WD-40 gunking up the works, causing the bolt stop to stick. You about gotta take it apart and sometimes it takes steel wool, etc. to get that varnish off the parts. Blasting it with brake cleaner, etc. usually doesn't cut that stuff.
Use WD-40 on farm equipment, keep it away from padlocks, guns, anything with small parts that interact.
DF
I've bought several Remington 721's, 722's and 700's with that problem and a good spray down with one of the crud cutter formulations with a little application tube while you work the release will usually free it up. You have to get it down in the little slot where the bolt release pivots and underneath the slider alongside the trigger housing. It make take several applications and be sure to wear your safety glasses/googles because those little nooks and crannies tend to spit the stuff back at you.
