The editors of the corporate website have reported there was a wrong language content on EN version. Once it was Chinese and a couple more times it was German.
I have experienced the issue just once so it looks like a really rare issue, but I was able to take at least some screenshots.

https://www.magnolia-cms.com/library.html

The rest call for the EN content looks like this https://www.magnolia-cms.com/.rest/library/ and it should deliver the English content. Like on the picture below.

The issue looks like this:

For comparison, a call for DE content should look like this:

I tried to reproduce the issue but unsuccessfully. As I said, it's occurred just once for me, simply by hitting the refresh button.

Here is the linkManagement config.

For now, I've changed the rest call so it contains a language parameter also for the EN version (/?lang=en) and we will be monitoring