Don't know why? I've tried with my physics entity several times
with different size of models, it passes them smoothly. May be I
post my physics entity setting below, see if it can help.

var GRAVITY[3] = 0,0,-386;

phent_settype(my, PH_RIGID, PH_BOX);
phent_setmass(my, 5, PH_BOX);
phent_setdamping(my, 50,50);
phent_setfriction(my,0);
phent_setelasticity(my, 0,100);
ph_setgravity(GRAVITY);