Throughout the time the engine gets a lot of updates. There's usually no major problems with the new content being added, but when something existing is being changed or removed - old dependent stuff can easilly get broken. This time Valve changed something in the DT system deeply in the engine, which caused all previously recorded demo files to crash with the following error:

The issue is still not fixed for now, so let's hop into the method of reverting the update with advanced steam techniques.

Let's quickly jump into the solution:

1) Run steam://open/console from Win+R while steam is opened
2) In the console type:


3) Wait for the depot to download, it will show no signs until it's ready. Then the following message will appear:


4) Back-up the following files in the Team Fortress 2 game folder:

5) Replace them with the ones from depot directory. Launch the game and voi-la, old demos are fixed.

Replace them back with the originals if you want to play the game normally with the latest version.

Well, then you'll need to find up-to-date pre-update manifest id here and do the same as described above. The update tracker is here - https://steamdb.info/depot/232251/history/


As mentioned in the comments by Thespikedballofdoom, you should download these depots (entirely) and merge them in one folder. You can launch the game with no internet or by replacing the version file (so Steam won't try to download an update).

pre_smissmass_2022_demos

pre_jungleinferno_demos