SmartUPS X 1500 Makes loud THUD. Shakes wall...afraid it is going to blow up.

[Anonymous user]

I am on my second 1500 unit. The first one started making the thud and then one day went nuts like an earthquake. I pulled the power and the battery connection in order to stop it. I have since dismantled the unit. Now I am on a second unit and it is starting to do the same thing. Has anyone seen this before? The only thing that I can think of that may have had an impact on the first one is that it was on its side at the time. Not in a rack. Are these units not allowed to sit on their side?

Thanks,J!