It is likely a slow leak from a pressure seal. This can happen because of dry rot, or an improper lubricant got into the seal, or just because it was not swapped out after its expiration date.
“It is likely a slow leak from a pressure seal. This can happen because of dry rot, or an improper lubricant got into the seal, or just because it was not swapped out after its expiration date.”
Why wouldn’t a leak generate a cabin altitude alert light in the cockpit and cause the oxygen masks to deploy?