Start the Editor.
Insert a Rifleman as Player (BLUFOR/Blue/Men/Rifleman).
Click on the Preview button.
go into a low crouch position (the issue does not appear to be present whilst in standard or high crouch)
while jogging forward, hit the vault key (default V)
observe that the player will dive to prone (possibly through/into the object to be vaulted) before standing upright to perform the vault (this can be repeated anywhere, you just won't observe diving into the vaulting object if there's no object to be vaulted over, but moving to prone before standing remains consistent)