Quick answer: Unreal Enhanced Input modifier key (Shift) stops modifying actions when key-up event arrives mid-frame? Modifier evaluation per-tick; held state matters at evaluation time.
Shift+W = sprint. Release Shift mid-W; sprint stops as expected. But W continues; same release event marks both released.
Use composite bindings
ButtonWithOneModifier composite. Modifier and base evaluated together; cleaner state.
Or check modifier in handler
Read modifier state explicitly; don't rely on action shape.
Audit modifier patterns
Each modifier-using action; document expected behavior.
“Modifiers are stateful inputs. Stateful needs careful handling.”
If your input has modifier-based actions, the composite binding pattern is standard. Document.