In the Link-to links, case sensitivity is distinguished. This means that if your link is "link-to/Custom Word", then "link-to/custom word" will lead to an error page or another destination.

However, you can make both work by editing the link to accommodate different options. This happens because when you edit the link, older versions of that link still work. For example, to make both of the above links point to the same destination, first shorten the link to "link-to/CustomWord", and then edit it to "link-to/customword".

Editing the link connects data for all versions of the link.

What about the URL address of the page with the link in the biography?
In the URL address of your Link-to Link-in-bio, case sensitivity is also distinguished. This is the link you create to share your Link-in-bio page with your audience.

You can change the URL address of your Link-in-bio page if you don't like the case sensitivity. Just remember, this doesn't work like redirection. You need to update all links to your Link-in-bio page wherever you've shared them.