Try browsing to the '..\Documents\Larian Studios\Divinity Original Sin 2 Definitive Edition\LevelCache' folder and delete the contents. A corrupt file there can cause problems when saving or loading.
Try exiting out of the Steam client, if applicable, and starting the game directly from the '..\SteamApps\common\Divinity Original Sin 2\DefEd\bin\EoCApp.exe' program file, by right clicking and running as administrator.
Try starting a new game, make a manual save after character creation and reload, then reload a save from your current playthrough. Moving a bit from the initial character position can trigger an auto save, which might overwrite one from your current playthrough. If you don't already have an honour mode difficulty save, starting one would avoid that problem, since it uses a separate, single save slot (in the difficulty list, after selecting Tactician there is a choice between Regular and Honour).
If the character dies in a new game, as well, create a new profile, start a new game, can see if you can save and load properly.
If a new game in a new profile also has this problem, try doing a clean boot and then test the game. Click Start, or hit WinKey-R, type in msconfig and hit enter; in the General tab, click Selective Startup, uncheck Load startup items (if required) and leave Load system services and Use original boot configuration options checked. Next, click on the Services tab, check the box to Hide all Microsoft services, then click the Disable All button (maybe make a note of which are currently enabled/disabled), then click OK and reboot the computer.
Run msconfig again to switch back to the normal boot configuration.
If that doesn't help, please email supportdos2@larian.com with your latest save (or a Dropbox or Google drive link, etc). Also include a list of mods enabled and/or the modsettings.lsx file from your profile folder (with the mods re-enabled).
Each save is a folder in the '..\Documents\Larian Studios\Divinity Original Sin 2 Definitive Edition\PlayerProfiles\<ProfileName>\Savegames\Story' folder.
In Windows Explorer you can zip a file or folder by right clicking on it/them and selecting 'Send To | Compressed (zipped) Folder'.