I have been able to reproduce this issue and have determined the cause of it. The issue is that when configuring the linked properties for the job type (screenshot 3), if you just check the field in the tree view on the left-hand side without actually clicking on that node, it does not correctly set the display type. This means that it is displaying this field as a Text Field. However, when it this tries to validate the field, it sees it is really a domain and tries to validate it as such and fails. This causes the error message you experience.
You should be able to resolve this issue by editing the job type, selecting the field in the tree view, confirming that it shows "Domain" as the Display Type, and clicking OK to save the update. I will also log a bug in order to resolve the underlying issue in future releases.