I marked this bug as reported on the 20th of July. I don’t normally explain server vs client update issues or the submission process.
I can’t reproduce the issue you’re having with the filter on 5.1.
The text only saves if you click “save filter” not if you click “apply filter” without saving it.
Maybe clear your filter, save it, then enter the filter you want to save without any text in the search bar, maybe you accidentally saved text in there.