@zepiczorua: If you have that problem on all assets, you most likely forgot to use required override settings at umodel start screen. But some of assets are encrypted anyway.
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Quickbms script for extracting game packages is added to specific scripts bundle, available
here (for more info read
sticked topic). It allows you to extract all assets from game paks with proper decryption. Tested on outdated build though, but it should be compatible with the latest version as well.
Special thanks to Gneiss for the key.