We have just added BVN 404 module to a new site (latest version) we are building.
It seem like when we use a static html 404 page it loads immediately. However when we use a custom 404 episerver page it takes about a minute to load.
There are some suggestions in post below but it does not seem to help
The redirects we are setting up in the module seem to be working fine and loading immediately.
You might want to consider raising this as a bug on the project and/or have a go at fixing it. It looks like there are some others who may be experiencing similar issues:
Thanks for your reply. Have just managed to figure it out
In order to resolve the issue you need specifically turn global error handling off