Fix bug #541 #542 (#545)

* fix #541 #542

* Update train.py

Co-authored-by: Glenn Jocher <glenn.jocher@ultralytics.com>

train.py

@@ -377,7 +377,7 @@ def train(hyp, tb_writer, opt, device):
 
                 # Save last, best and delete
                 torch.save(ckpt, last)
-                if (best_fitness == fi) and not final_epoch:
+                if best_fitness == fi: 
                     torch.save(ckpt, best)
                 del ckpt
         # end epoch ----------------------------------------------------------------------------------------------------