Delete Unused Labels fails with 500 error

Hi all,

Jira 8.20.11 + zephyr scale 9.27.

Test library / Configuration / Labels.

The first problem. Labels list opens for 12 seconds. And very slowly scrolls.

Click on "Delete unused labels" link, confirm the question.

The second (and main) problem - "Oops! Something went wrong".

And I get the "500 error" from nginx proxy on "/rest/tests/1.0/label/deleteUnusedLabels" request.

Any ideas how to fix it and delete all unused label finally?