My 2002 Protege had the issue in the rear doors since nearly new. I ran that car 12 years and 150K miles without the door lock actuators ever failing.
Wife's 2009 Mazda6 has the issue in the rear doors and occasionally each front door and has had the noise(s) since it was nearly new. Running almost 7 years and 60K miles without actuator failure.
My 2015 Mazda3 hatch has the issue cropping up on the driver's door occasionally. It's only nine months old (nearly new in other words). It has 15K. Based on past experience, I'm pretty sure it's just a noise and won't fail.
Is it annoying? Maybe. But is it an indication of impending failure? Not likely.
Think of it as a 'feature.' A very strange somehwat annoying Mazda-only feature.