This is a sample firebase storage url:
When shortened the url saved in the db is with "/" instead of %2F (after images token).
Firebase domain return 404 for those links.
You can remove the encoding of the url in includes/functions.php, at the function "yourls_add_new_link".
Just remove the two rows which makes encodeURI and escape.
Don't Hack Core!
This should be tweakable with a plugin, or perhaps YOURLS should not be decoding entities in URLs like this one.
ok so fix needed