Our QA teams are still testing the 4.1 version, but we don’t anticipate any performance loss in the new release. To take a wild guess, you may be experiencing hitches caused by out of date Derived Data Cache. This is the cache of compressed textures, audio and meshes that is created on demand by the engine when assets are loaded for the first time since a big engine change. However, these hitches should vanish after the first few runs as your cache should be up to date with fresh data.
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