hello,

I was on your site - This look like issue with database cache. language change did not cause changes in the database cache.
Probably it was a single bug because I made a test message on your forum and everythings works good (post edit etc.). - not this message is deleted of course.

For this single post when each edition of this post, the cache in the database has not been overwritten
Now - it looks like solved - the addition of a single stamp (like space) has forced the re-entry in the database cache (of course message is still in original form - you can check - just edit a post). And after this re-entry your post is translated good.

At this moment I can't explain what was wrong with this single bug - maybe temporary lack of connection to google.
If this happens again and If you can reproduce this bug again - just describe it step by step and I will try to reproduce it on my test forum and solve.