can't access files with percents in filenames

Confirmed.
Tested on version 5.x/6.x/7.x.

Any suggestions to solve this issue?

i think the transliterate module would help work around it. but #238299: file_create_url should return valid URLs might address this directly.

marked #154245: problem with filenames with '%' character as a duplicate but since it actually has a patch i'll mark this as a dupe of it instead.