There are three problematic media wiki messages: "cite error references duplicate key", "cite error references missing key", "cite error references no text" that become unreadable in non-ASCII-languages. The text

Invalid <ref> tag; name "թ" defined multiple times with different content

is shown as

Invalid <ref> tag; name ".D5.A9" defined multiple times with different content

Meaning, we can see uri-encoded text in place of unicode symbols.
It can be fixed on each Wikipedia locally using a module with

return mw.uri.decode(frame.args[1])

a template ("decode") invoces it, and changing $1 in media wiki messages by

{{decode|{{replace|$1|.|%}}}}

but I ask you to fix it in PHP, possibly using one more field in reference data structure - original text.
Thank you very much in advance.