Yup.
Happens when you combine ammo with no primer sealant with a gun that's been over-oiled and/or improperly cleaned. Oil vaporizes and sneaks in around the primer, rendering it inert over time.
For guns you keep loaded, clean & oil them, then run a dry patch through the chamber(s) and bore to remove excess oil. Dry fire the gun (except rimfires) 5-6 times to see if the action oozes more oil. If so, blow out excess with compressed air & wipe gun down.