The current PTR has the steam-cloud autosave system enabled.
We recommend that you back up your saves - copy the folder Cache > C:\Users[Username]\AppData\LocalLow\CarX Technologies\Drift Racing Online\Cache to a separate location.
Make sure the checkbox "Enable the Steam Overlay" is checked in the game settings in Steam.
Also, before the release publication of the PTR branch, we recommend that you stay in the current version of the PTR to reduce the likelihood of losing progress.
PTR 2.13.4 V1
Source: Steam Community (opens in a new tab)