Can you ensure the content is not being cached in your browser? The default browser cache expiry is 12 hours and I've noticed it can appear that content is not updated when re-uploading assets.
Thanks for your reply, but unfortunately I have checked this and it's not a browser cache issue.
In that case your best bet is to register a developer support incident here: https://world.episerver.com/support/. If the issue can be replicated on a standard Alloy site running the latest version and using your steps then it should be accepted through triage and added addressed in the bug list.
The file replace function is not working.
Steps to replicate: