This happen to me with a lot of instance of WordPress, but I didn't undestand at what moment exactly the translated "String translations" of polylang are resetting.
Now I've found that when I have a translated string (that I've already translated); if I delete the original string, I'll not find this sentence in the "String translations". Thats OK.
But the bug is that, after deleting one "String translations", many others "String translations" are resetting to the original status. Like if I've never translated them.
So I always re translate this sentences again again every each deleting of "String translations".
Does anyone has already faced this issue ? How can we solve it ?