Can you provide an example?

Thanks for the reply!

Go to https://ro.wikipedia.org/wiki/Pagina_principal%C4%83 (Romanian Wikipedia)

Make sure you have a registered Wikipedia account and you are logged in.

Click in the top-right bar: "Contribuții", then select "Traduceri"

Click the green button labeled: "Începe o nouă traducere"

In the first field (Din) type something like: "Stealth aircraft"

In the second field (În) type the name of a personal page: "Utilizator:Your user name/Stealth aircraft"

Click "Începe traducerea"

Add a few paragraphs, any would do.

Click the green button at the top-right, labeled "Publică traducerea"

The interface should hang for about 20 seconds and end with a 503 error:

"A apărut o eroare la publicarea traducerii. Încercați să publicați pagina din nou. Eroare: parsoidserver-http: HTTP 503"

The translation is a prisoner of the interface with no way to even extract the raw wikitext to manually publish it.

I hope that helps. ^^

Jobava

Attempting to translate [[:w:en:Salmon P. Chase|Salmon P. Chase]] from English to Romanian, and [[:w:fi:Venäjän–Turkin sota (1735–1739)|Venäjän–Turkin sota (1735–1739)]] to Romanian generated the same error.

Replicated successfully while translating the article https://en.wikipedia.org/wiki/Nityanand_Kanungo from English to Gujarati. The error did not occur after we removed the references from the translation target.

More reports:

https://www.mediawiki.org/wiki/Topic:Sn96o0709mjg2uhv
https://www.mediawiki.org/wiki/Topic:Sn6pba8fttudkiky
https://www.mediawiki.org/w/index.php?title=Topic:Sn6pba8fttudkiky&topic_showPostId=sn8k2k2y7m7303gy#flow-post-sn8k2k2y7m7303gy
(possible) https://www.mediawiki.org/wiki/Topic:Sn2rvwnsbdtwayih
https://www.mediawiki.org/wiki/Topic:Smv7jdtidgeg0ewd

This might be T109659: paraminfo for contenttranslationlist is broken on beta wikis?
(however that doesnt explain why it is happening on production)

See T109574

English to French "Peștera cu Oase" -> was not affected by T109574 (see comment)

The error occurs only for the following article but not for any of the others mentioned in the reports:

https://fi.wikipedia.org/wiki/Ven%C3%A4j%C3%A4n%E2%80%93Turkin_sota_(1735%E2%80%931739) - translating from Finnish to Romanian

In the past few days, the count of 503 errors are zero