To reproduce:
1. Open the lookdev tab, open the single object split comparison view or Single object zone comparison view
2. Click on one of the ends of the separator, and, without releasing, press shift and drag
3. Notice that everything works as intended, the separator is movable and it snaps to a direction
4. Now try to do the same, but press shift before clicking
Notice that the separator is now impossible to move.

Expected result: The separator is still movable when doing step 4.

Reproduced on: 5.5.0b1
Not tested on earlier versions, because look dev is a new feature.