The issue is that we are attempting to filter on some values for which the hidden ids of those lookups contain special characters (specifically commas) and we are getting wrong results filtered as a result of this.
Release : 15.9.1
Component :
The most clean way to fix this would be to create new lookup where no special characters are used in the IDs, alternatively you can inactivate those value that contain special characters and create new ones that don't have them. Please note if you inactivate those values it will still display them for existing project instances but that value will no longer be available for selection.