It could be lots of things. Power is an obvious one. It could simply be the worm engagement is a bit off or the worm floats are tiny bit too tight.

How long have you had it ?
Has it ever hads any funnies before ?
Crucially how much have you used it ?

The reason for the last question is that if the worm engagement is off a bit you may have just been lucky in using it before and never hit the bit of the worm gear thats maybe a bit 'off'

Worm engagement can be swinish to adjust, its not hard but time consuming. End float adjustment is simple enough.

Oh - one other question - does it make the noise in RA or the DEC. The DEC motion is a lot easier to adjust.

If its in warranty I'd send it back. If out of warranty then I guess its either DiY or find someone friendly who has experience of the mount. They arent that hard to take to bits and adjust so long as your patient and have a small amount tool handling skill.