Zhumell Dobsonian telescopes' altitude bearings are attached to the OTA (Optical Tube Assembly) by two bolts on each bearing. These bolts, however, do not have lock washers on them, and they frequently come loose, sometimes after only a night of observing. This can be frustrating and even dangerous if one of these nuts were to fall onto your primary mirror.
The solution to this of course is to add lock washers or Loc-Tite, whichever you prefer. I preferred both, so I used both. I don't plan on ever needing to remove these bolts. This is a really simple mod, and can be accomplished in less than an hour and costs nearly nothing.
This should take care of your wobbly altitude bearing problems on any Zhumell Dobsonian. The telescope shown here is a Zhumell 10" Dobsonian.
Disclaimer: I cannot take any responsibility for any damages, to you or to your property, occuring before, during, or after performing this telescope mod or resulting from any advice taken from this website. Do so at your own risk.