Dynamic hostpool sessions not updating

We have created a dynamic host pool in a test environment. We see that new hosts are being created based on the scaling plan.

However, these are no longer being deleted. When we look at the status, we see that there are no active sessions, but when we zoom in on the session hosts, it shows that there is a session on two of the three hosts. The latter is incorrect, but it is likely the reason why scaling down is not taking place.

Does anyone recognize this? Is there possibly a solution for this?

Small addition: If I log in with a user and then log out properly, the current sessions in the host pool overview are updated quickly. However, if I then go to Manage, Session Hosts, the total sessions on that host remain at 1.

When I now put the host in drinamode, only then are the actual sessions updated.