Following the release of the Anniversary Edition (AE) in 2021, Bethesda updated the base game binary, breaking many popular script extender (SKSE) plugins. As a result, many users actively downgrade or maintain their installation at .

Unofficial Skyrim Special Edition Patch.esp (This must be the very first non-Bethesda mod in your list).

: Extract the downloaded USSEP 4.2.5b archive (using 7-Zip, WinRAR, or similar).

Go to the page on Nexus Mods. Check the Miscellaneous Files or Old Files sections.

This method replaces your SkyrimSE.exe with the 1.5.97 version but keeps the new Anniversary Edition content and plugins ( .esm files).

To understand why a user would specifically seek a "1.5.97" patch, one must understand the dependency chain of advanced Skyrim modding.