Discovery/Inventory not running according to schedule

Hi,

I`ve been relatively successfully using OME 2.1 in a large environment, however since a while the scheduled discovery and inventory tasks fail to run. 

Only the following errors can be found in the application logs, which I believe are irrelevant: 

Discovery/Inventory settings look like this:

Yet when I go to discovery ranges  and click on a group, at start time and last updated I`m expecting to see a more recent date, not when I last ran it manually.

Any ideas?