How to reproduce:
1. Open the attached project "Bug_ProBuilder_Snapping.zip"
2. Select "Pro_CollidarStandard_Top" GameObject in the Hierarchy
3. Select the "Edit Shape" tool in the Toolbar
4. Click "Reset Shape" in the "Edit Shape" window that appeared in the Scene view
5. Hold and drag the edge of the GameObject in the Scene view
6. Hold and drag the opposite edge of the GameObject in the Scene view

Expected result: the increment is consistent
Actual result: the increment changes

Reproducible with: 5.0.3 (2019.4.34f1, 2020.3.25f1, 2021.2.7f1), 5.0.4 (2022.1.0b2)