H-Bridge shoot through at high voltage problem - Don't know the cause
As you can see, the PWM switch off, then a short delay layer, the HO tried to switch off but for some reason, it cannot sink it to ground and stay floating for eternity later.


HO is turning off. The voltage drops from about 184V to about 155V.
Check the left white circle.

LO is turning on very badly. Check the second white circle.
For best turn on, \$V_{GS}\$ should be monotonic increasing (like an RC-curve) to have the fastest turn on and, so, the least switching losses.
Next best, is the gate voltage increasing, stay for a small while at the miller plateau and then, increase further.
As shown in the right white circle, the purple gate voltage is dropping, causing the mosfet to return to linear operation or "ohmic region" making the switching losses very high.  

The reason of the gate voltage collapsing can be because it is not driven correctly.

From the comments, it appears the layout has separated grounds.
This makes the mosfet Q4 drive current has a very bad return path to the COM pin of the driver: a long path has quite some inductance (and also some resistance) which causes the gate the be driven badly.

Another reason to shorten the return path of this gate drive current loop is given by the bold emphasis: it is a current loop: the less area the loop has, the less it can radiate EM.