For the 2nd time this month the Jenkins list of lightweight executors on master is growing to several dozens idle entries (see screenshot).
Normally this list is shrinking again after these executors are done, but for whatever reason this size is heavily increased.
After a Jenkins reboot it's fine again.
Most likely it was fixed in 2.208 by JENKINS-57304. Please test this new version and reopen the issue if it is not fully fixed