Software Environment\Windows Error Reporting
taskkill /f /im "tabtip.exe"
cd /d "<path to the game>\Assassin's Creed Liberation"
The problem here appears to be the same as in Assassin's Creed IV: Black Flag. It is caused by lack of triple buffering in the game.
Don't force VSync in D3DOverrider, only triple buffering.
Enable VSync in game options (or force it in NVIDIA control panel or NVIDIA Inspector).
You can also try the other workarounds for Assassin's Creed IV: Black Flag.
The gain in framerate for the second fix is very significant and sustained as the loss of framerate seems to be related to Uplay synchronisations slowing the game down on slower/firewalled internet connections leading to highly abnormal drops as Uplay sync fails repeatedly. No progression-related in-game features are affected by this fix as no multiplayer is present in the game and Uplay unlocks are added by the Uplay client in a save outside the game.