Your mount is on our bench.
We noted some impact damage. That could've loosened the mesh, but it hasn't.
We didn't find notable backlash. Indeed, the mount is designed so that, even if the gearbox loosens, it is impossible to experience more than around 1.5-1.7mm backlash in the worm/wheel engagement (determined by the thread pitch). To experience more, the RA worm must be completely disengaged.
Where are you measuring 1 cm backlash? Perhaps you are measuring movement at the front of your telescope. I.e. if the mechanism has 1mm backlash, then this would equate to around 1 cm movement at a telescope objective 50 cm away from the pivot point. The actual backlash would still only be 1mm.
Anyhow, your mount is good, so we'll reassemble and return it to you.
HTH,
Steve