I also have the exacte same issue.
I just tested the last "Blocks" application demo on a PC i7 GeForce GTX 780 - Win7 Pro - 32Gb RAM. with Leapmotion on a front of Oculus Rift DK2.
When the device is cold, just plugged in, the tracking is working fine.
After a while, the device is heating up and gestures are not fully recognized, bugs appear.
And when it becomes very hot than the gestures are having a lot of unexpected gliches and the application becomes unusable.
Does my Leapmotion have a construction defect (as I noticed in ohter threads it should not overheat that much) ?
Do I have to replace it ?