Pasting a bugfix for the infinite validation loop here just so I don't lose it:

1. Open the folder where steam is installed

2. Open the "logs" folder

3. Open the content_log.txt file

4. Search for "failed".

5. Open the file location listed in your failed entry and delete the listed file.

6. Try updating again.

(Bugfix from https://steamoss.com/discussions/forum/30/6516193260173485339/#c5560306947037446253)

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