NeMo's BERT based intent slot classification model (nemo_nlp.models.IntentSlotClassificationModel) fails to train
NeMo's BERT based intent slot classification model (nemo_nlp.models.IntentSlotClassificationModel) fails to train (training loss remains the same after every epoch) when we use NeMo's stable versions (eg. v1.12.0, 'main' branch). However it trained perfectly well when we used the `r1.11.0` branch instead.

Please run this [Joint Intent Slot Classification](https://github.com/NVIDIA/NeMo/blob/main/tutorials/nlp/Joint_Intent_and_Slot_Classification.ipynb) notebook as it is to reproduce the bug.

 - Environment location: GCP Compute Engine (NVIDIA T4 Tensor Core GPU)
 - Method of NeMo install: 
       `BRANCH = 'main'`
       `!python -m pip install git+https://github.com/NVIDIA/NeMo.git@$BRANCH#egg=nemo_toolkit[nlp]`