Validation Loss as well as validation F1 increasing

Hi,
While finetuning scibert on JNLPBA and bc5cdr dataset, I observed very strange phenomenon.
The validation loss is increasing whereas the validation F1 in either increasing or staying the same.

Please let me know because I have faced a similar issue when I used pytorch-crf over scibert. There also for ner (JNLPBA and bc5cdr) validation loss anf validation f1 are increasing.