After clicking on reference link, popup (black box at the bottom) will shown on a second with loading bar and immediately disappear. Bug replicated only when enabled Wikipedia Beta features at mobile Settings, on references, which ref name attribute contains Cyrillic. Here are some examples:
https://en.m.wikipedia.org/wiki/User:Serhio_Magpie/sandbox - references #1.
https://ru.m.wikipedia.org/wiki/Большая_российская_энциклопедия_(издательство) - references #1 and #4.
https://ru.m.wikipedia.org/wiki/Белокопытник - references #12 and 13.
https://ru.m.wikipedia.org/wiki/Узбекский язык - reference #1.
https://ru.m.wikipedia.org/wiki/Савинова,_Екатерина_Фёдоровна - references #2, #3 and #5.
https://ru.m.wikipedia.org/wiki/Дорога - reference #1.
Screen capture: https://www.dropbox.com/s/za692cgqjf0nf9s/wp-beta-references-bug.mov?dl=0