The shirt models in TR_Data are still not adapted for Better Bodies (or Robert's Bodies) which I would say have become the standard in a modded game nowadays, simply because they are better. This is particularly evident for the female models, where the model used in TR is clipping into the skin at the neck. The models in PT_Data (which are also commonly used in Tamriel Rebuilt) use better-bodies aware meshes, so this should not be too difficult to implement. The affected female models are (as far as I can tell) TR_c_shirt_com_cf_07.nif, TR_c_shirt_com_cf_08.nif, and tr_c_shirtcom_001_cf1.nif. The number of male models is much larger, but I think it should be fixed also here in future.