It seems that after a lookup that is in DropDownMode is initialized changes to the LookupPrefilters have no effect. The items are cached and a check is done to not reload the list if any items exist in the list. Since the list is cached a new call to LoadItems will not be made.
Luckily with a little reflection magic this can be resolved. The following code is a method that can be called that will clear the items and allow it to be correctly refreshed in case of a change to the LookupPreFilters
Have an excellent day
Thanks! I was wondering what was going on here…..great solution.
In 7.5.4 new methods have been added to clear the cache on the lookups and dependency lookups. It will make it easier to do this without Kludging the code.