[#7065] Username format -> This profile does not exist or is no longer available

We're encountering errors when trying to view profiles of users with all-number or starting-with-numbers usernames. In our case the profile urls are like this:

sitename/component/comprofiler/userprofile/*
sitename/me/profile/*

* can be numbers only or starting numbers followed by a dash

Error
This profile does not exist or is no longer available

These profiles are accessible when using the user ID instead of the username.

Now, is there any good way to filter for this when users sign up? (I don't speak regex)

Joomla! 3.8.5
CB 2.1.3 (can't update yet, need to test on clone site)
PHP 7.0.27
Joomla URL rewriting on

Please let me know if you need any further information.
Apologies if this has been posted before, I couldn't find relevant topics.

Users profiles that can be accessed by username have a URL safe username. Those that can't don't have a URL safe username and will have their profile URL prefixed with their user id. This is all working as intended and can not be filtered out. To avoid this you can allow users to use the Profile URL (alias) field where they can supply their own name to be displayed in their profile URL, which will be saved as URL safe so it'll always work.

Thanks, Kyle. Sorry, but I'm not sure I understand correctly.
Wherever there is a link to these users' profiles (in kunena, online users module, newest user module etc.) their profile is linked using their username as above and the profile can't be accessed. Their profile URL is not prefixed with their user id. Is there a setting I'm missing?

I've no idea what'd be doing that then. Are you using a 3rd party SEF extension? Is CB completely up to date? The user id should only be prefixed if it needs to be.

Joomla's own SEF only. Everything's up to date, except CB 2.1.3.

I just double-checked and saw that numbers-only usernames do get the ID prefix as you described. The username that isn't working for: 24-bit

Update CB and see if your issue persists. I don't know what to suggest. We turn a username into a URL safe alias using Joomlas own routing functions. If the username doesn't equal the new URL safe username we prefix the user id since we won't be able to match it to a user. If they are equal then user id isn't prefixed since we can match it to a user. Do any of our products have issues linking to profiles or is it just other extensions we didn't develop as it could be a matter of those extensions constructing the URLs incorrectly.