Stalled metrics are not reported for backward model

[eu9ene]

The bleu/chrf/ce-mean-words_stalled metrics are supposed to be on the online training dashboards but they are missing.

https://wandb.ai/moz-translations/zh-en/runs/backwards_E8S5g?nw=nwuserepavlov

I do see the messages in the log https://firefox-ci-tc.services.mozilla.com/tasks/Q5CG-D5kQaqZQGYukCsrcg/runs/1/logs/live/public/logs/live.log

[task 2024-09-13T16:39:03.768Z] [2024-09-13 16:39:03] [valid] Ep. 1 : Up. 360000 : chrf : 31.403 : stalled 2 times (last best: 31.8198)
[task 2024-09-13T16:39:05.636Z] [2024-09-13 16:39:05] [valid] Ep. 1 : Up. 360000 : ce-mean-words : 2.46139 : stalled 2 times (last best: 2.45698)
[task 2024-09-13T16:39:19.532Z] [2024-09-13 16:39:19] [valid] Ep. 1 : Up. 360000 : bleu-detok : 35.3306 : stalled 2 times (last best: 35.4744)