Good info from Henderson Defense over at an archived AR15.com thread. HD is one of the machine gun rental ranges in the Las Vegas area. They go through something like a million rounds per month and have posted about their experience with high round counts on various platforms.
The Uzi-specific info starts at post #9 of the thread. Note that these are converted post sample machine guns. The backplate welds seem to be the primary issue, and they note that the welds on their Century Arms guns are notably smaller than those on IMI guns.