Sure. And the minimal repro 6 is updated at the same time.
The result, got frozen after validation:
16:18:13 723869     | Rank:1 - Epoch 0/24
16:18:13 723866     | Rank:0 - Epoch 0/24
16:18:13 723900     | ----------
16:18:16 888776     | Rank: 0 - train Loss: 0.5663 Acc: 0.6885
16:18:16 896916     | Rank: 1 - train Loss: 0.5002 Acc: 0.7705
16:18:16 896992     | Rank:1 waiting before the barrier
16:18:17 383175     | Rank:1 left the barrier
16:18:17 383215     | Rank:1 - Epoch 1/24
16:18:17 829886     | Rank: 0 - val Loss: 0.2327 Acc: 0.9150
16:18:17 829934     | Rank:0 waiting before the barrier
16:18:17 830029     | Rank:0 left the barrier
16:18:17 830044     | Rank:0 - Epoch 1/24
16:18:17 830051     | ----------


I change the validation function to time.sleep and the barrier works fine:
16:40:57 446421     | Rank:1 - Epoch 0/24
16:40:57 446420     | Rank:0 - Epoch 0/24
16:40:57 446456     | ----------
16:41:00 635462     | Rank:1 - train Loss: 0.5516 Acc: 0.6885
16:41:00 635536     | Rank:1 waiting before the barrier
16:41:00 635599     | Rank:0 - train Loss: 0.4810 Acc: 0.7705
16:41:00 635663     | Rank:0 sleeping
16:41:05 640713     | Rank:0 awaken
16:41:05 640734     | Rank:0 waiting before the barrier
16:41:05 640875     | Rank:0 left the barrier
16:41:05 640890     | Rank:0 - Epoch 1/24
16:41:05 640882     | Rank:1 left the barrier
16:41:05 640912     | ----------
16:41:05 640935     | Rank:1 - Epoch 1/24
16:41:08 641714     | Rank:1 - train Loss: 0.3519 Acc: 0.8279
16:41:08 641790     | Rank:1 waiting before the barrier
16:41:08 651248     | Rank:0 - train Loss: 0.4229 Acc: 0.8156
16:41:08 651340     | Rank:0 sleeping
16:41:13 656394     | Rank:0 awaken