One difference may be a change in the tpusr file. If you have not applied a patch then please apply the latest rolling patch level available for your platform,
recreate the tpusr file, and rerun your test(RP001 has a change for tpusr but there are some other security related fixes in later RPs which you may also want).
Otherwise, open a service request and provide an example/testcase/reproducer/steps to recreate.
There are many Tuxedo 12 rolling patches listed on the My Oracle Support website.
Following is an Oracle knowledge management (aka KM) document with instructions to locate one (i.e. choose the highest RP# available for your platform):
Tuxedo Patches Can Now Be Directly Downloaded Without Having To Open A Service Request NOTE 1075805.1
Let me know if you have any problems. (If so let me know the platform you are looking to find an RP for)