The intermittency of this high frequency jitter on LX caused by load condition and temperature change implies this is a board related noise issue. The resolution of using shorter wire connection from DH to MOSFET gate proves the driving trace is impacted by the noises. It looks like either the driving trace to MOSFET gate is laid out too long and it picks up too much noise from the board in certain circumstances, or the power stage is laid out in a way that noisy source (for example switching node) is too close to the driving path.