I don't think you're going to find any argument here about the rings being cheap. They certainly are, but leaving the mounts (which is what I understand "popped off" to mean) strikes me as a new phenomenon.

The first possible explanation that springs to mind is perhaps the rings were not fully seated on the mounts. It is possible for Weaver rings to tighten without the cross bolt actually running through the grooves in the mount. My response to this would be to loosen the screws holding the scope in place and, with the rings moving independently, verify that they both seat on their respective mounts before tightening the cross bolts and then re-tightening the other screws.

When you say all the screws were tight after it popped off, does that also mean the cross bolt was bottomed out against both the clamping element and the bottom of the ring? If so, that would indicate something is out of spec. Get your dial calipers and measure the maximum width of the mounts from edge to edge. Then crank the ring's cross bolt down tight against the clamping element and ring body and measure the corresponding distance under the ring. You can look up the specs for a Weaver rail online if you like, but if the maximum mount measurement is smaller than the minimum ring measurement, then you've got a problem irrespective of the actual specs. Either way, it should be taken up with the retailer or factory.