I'd say always call too.
This kind of scenario reminds me of an incident I witnessed a good few years back. A small turboprop was waiting at the holding pt. behind an A320. The pilot of the turboprop told ATC that the A320 had a hatch open just below the R2 door. The A320 pilot requested a return to stand so an engineer could investigate. A few minutes later the A320 called up ATC to say it was the cabin air outflow valve, and is usually open on the ground.
Needless to say there was red faces all round.
However, 'if in doubt, shout!'.
MB