I have a simple cube over the floor using the POLY flag:
Code:

---

 
 phent_settype(ent_poly, PH_RIGID, PH_POLY);	
 phent_setmass(ent_poly, 0.5, PH_POLY);
 

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this code works on 6.31 but on 6.4 the cube sinks on the floor.
I have a simple project test to reproduce this bug.
Any ideas?