I am experiencing the same exact behavior as described in this thread:
Strange behaviour Skillbuilders super lov in APEX 5
Entering a search string in the super lov and either pressing the search icon or pressing TAB, the lov page behaves as expected.
If I press ENTER instead, the lov modal pages appears for a split second and then disappears and it appears as if the page submits because the validations for the page fire.
I have several super lov's in use throughout my applications and only one exhibits this behavior and it is on a modal page.
The workaround suggested in the thread is not applicable to me because I do not have the lov mapping to any hidden page items.
I have tried deleting and recreating the lov, moving the order of it on the page and the behavior persists.