Ties sometimes do not respond to Inspector offset adjustment until editing completed
OS: Windows 10 (10.0), Arch.: x86_64, MuseScore version (64-bit): 18.104.22.16852, revision: a9df4a0
Open the attached file and take the reset. Click on a note tie and use the Y-offset in the Inspector to move it downwards.
Result: It stops at 0.5sp. If you move it beyond that point, then press [Esc] (or click on a blank space), the tie will suddenly jump to the new position. You have to save and reload the file to restore correct functioning.