DeepRoboticsLab/rl_training

AI Summary: The user encountered a `ValueError` during `train.py` execution because `contact_forces` sensor configuration failed to find `_FOOT` links, which were seemingly absent from the USD model generated by `urdf_to_usd()`. Setting `merge_fixed_joints=False` in the converter resolved the error, implying that these links were being consolidated when fixed joints were merged. The user is seeking clarification on whether `merge_fixed_joints` should be `False` by default for their model, or if this workaround points to a deeper issue in the conversion process or sensor configuration.