Hello Ben!
thx for your reply.
and now the problem has been solved.
the issues is all about the deforming attribute in bullet solver.
because at the beginning of the animation. i create the deforming and active attribute by wrangle.
but when u use deforming attribute in DOP. it looks like that the bullet solver will not inherit the orientation and transformation data from SOP to DOP. all the orient and transform attribute is ZERO when the active is 0.
and i have checked the RBDtoFBX rop. it looks like they will use the packed point to transform the original geometry then export.
so when the packed point don't have any transform and orient data. it will cause the problem.
so the issue has been solved by switch the deforming attribute to animated attribute.
Hope this will help someone!
cheers!
Kong