Some processes (chrome based) not working without watching them

We are having a strange issue with a couple of our processes automated in Google Chrome (although this may not be relevant).

For some reason the process doesn’t work when run unattended from orchestrator. When we log in to the exact same robot and instead run the exact same process, with the same queue items, on the same robot but run it from the robot tray when logged in, it works fine?!?

Does anyone else experience this problem?

Just to add:
The error message that appears when run from orchestrator is not finding a selector:
Process execution ended with exception message: Cannot find the UI element corresponding to this selector

And an obvious point, yes the robots we have are unattended robots.