Solved: DD-WRT upgrade failed

When updating the DD-WRT firmware of your router, the message “upgrade failed” or “update failed” appears. The problem is related to the browser you are using.

In 99% of cases, the problem can be solved by using a different browser. Chrome in particular is often susceptible here. I never thought I would say this, but: “For the first time, Internet Explorer has a raison d’être other than downloading other browsers”.