If you don't know how to use the editor correctly - yes.
There are certain fields/values that you can change and others that you cannot and if you change them they will corrupt the USER.DAT file. I figured this out the hard way long ago making 1 change then saving and trying to load, then another, then another. I also learned to make regular backups of working USER.DAT files because even when you know what you are doing it's still possible to make mistakes and corrupt the file.
There are fields/values that have string pointers in the code and only the game can change these string pointers. It means for some players, to get the string pointers to change you actually have to achieve that by doing that in a match in-game and seeing it through until the game ends and the game updates the string pointers for the USER.DAT file. Then you can proceed to edit their stats as you like.
An example would be the B.B.I field if someone has YTB or 0 for 9 you can't change it to 10 for 9 or 10 for 10 because it's a different number of characters/digits which require the string pointers to be changed - something the game can do but the editor cannot.
One final piece of advice. After each change you make (once you know what you are actually doing and how to work the editor properly that is) save the file, close the editor and open it again. If you try to change multiple things for different players (for example several first names/surnames in particular) the editor will corrupt the USER.DAT file when you save. However, if you make a change, save, close the editor, test and backup your USER.DAT file each time you will gradually learn how to operate the editor and avoid these issues and exactly how much you can change before saving. In my experience, it's possible to change a full team of players' skills then save but individual changes like names, heads/skin tone and stats should be done one at a time, save then close the editor and reopen. I will even save and reopen for one individual player after changing the first name before changing the surname as trying to do both in one go can cause corruptions too.
Hope that helps, I spent a lot of time doing trial and error to figure this stuff out when creating the Ashes 2019 Mod.