This version is not backwards compatible . Saves created or opened in 1.39.5 cannot be used on older versions of the game, so it is recommended to back up your save files before updating.
You can use tools like [Switch Army Knife (SAK)](github.com dezem/SAK) to merge your base game NSP with the update and DLC into a single file for a cleaner installation. Version 1.39.5 Highlights Astroneer SWITCH NSP [Update] (eShop)
Download the specific Update NSP file corresponding to version 1.39.5 and install it using a tool like Tinfoil , DBI , or Awoo Installer . This version is not backwards compatible