An "exclusive access" error generally occurs when the operating system prevents a program from opening or modifying a file because another process has already "locked" it for its own use. For Vintage Story players, this usually manifests in three scenarios:

Understanding the VintagestoryLib.dll "Exclusive" Error and Game Architecture

Avoid downloading standalone DLL files from unofficial third-party sites, as these are often associated with security risks. If your file is corrupted, use the official Vintage Story full installer to repair your installation.