An attempt was made to start another test even though a test is already running.

e.g. automatic duration test underway and manual function test is started. 

Multiple attempted starts are also possible via the timer.

If the program hangs during the test, you have the following options:

1. Wait 24h to see if the check ends by itself.

2. Restore a backup in which this problem did not exist.

3. Reconnect all devices.