Field object lists in ALM 11.52

Hi,

since migration from QC 10.00 to ALM 11.52 we have problems accessing lists of field objects.
For example: I created a project list "MyList" and a defect field "MyLabel" (project entity -> Defect->User Fields->"MyLabel", name "BG_USER_01", type Lookup List, attached to "MyList").
In QC 10 in workflow script "Function Bug_FieldCanChange" I was able to get the attached list by using "Bug_Fields(FieldName).List".
In ALM 11.52 the script never returns the attached list, but the command "Lists.List("MyList")" to get the list directly works.
Does anybody know how to get the attached list of a field object or if something regarding lists has changed in ALM 11.52? Thanks!

Best regards,
Christoph