If you zip the lsv file in the save folder, does the size decrease significantly? It is already compressed, so if zipping it reduces the size by very much it would imply that it is corrupt and there is missing data in the file (one or more sections replaced by zeros, for example).
You can also check the save using an
extractor program, if you wish (
download).
After unzipping the download somewhere and starting the ConverterApp.exe program, switch to the 'PAK / LSV Tools' tab, and at the top under 'Extract Package', in the 'Package path' browse to the save's lsv file, then for the 'Destination path' browse to that or another profile's '..\savegames\Story' folder and enter a new folder for the extracted files (you can copy/paste the path from the path listed above and edit it; ie to be '..\Story\save_extracted') and click the 'Extract Package' button. This will give an error if the file can not be recognized as a save, or if the contents can not be extracted, or the size or checksum value of the data do not match what is listed for the corresponding file in the archive.
Alternately, if you zip the save folder and email supportdos2@larian.com with it (or a Dropbox or Google drive link, etc), I can check it.
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' (and similarly in OSX/Finder).
