I have managed to replicate this issue.
The same is happening if you open the user details in a new tab.
There should be something wrong with the dots andI have got the same error when I created a username with two dots.
Also you will be able to access the page if you change the last part of the URL to “mathias.kallbergatfootwayco”
I have found the bug and it’s in the routes, could I just create a PR to fix it?