When exiting a packaged project with the Bink Media plugin enabled, a fatal error is shown. This does not occur in packaged projects without the Bink Media plugin enabled.
The Bink Media plugin does not exist in 4.26, so not a Regression.
A fatal error message appears after closing the packaged executable
There would be no fatal error shown when closing a packaged project with the Bink Media plugin enabled
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-125141 in the post.