Hi @Alexey_Demyanchuk, you are right!!
Thanks for help me!
Adding this into my fit method between model.train() and the loop:
# *** TRAIN ***
model.train()
for module in model.modules():
    if isinstance(module, nn.BatchNorm2d):
        module.eval()
for xb, yb in train_dl:                     # iterate every batch

I can fix my inconsistency.
Thanks again