instrumental plural *wĺ̥kʷōys
Не знаю, с чего Вы взяли, что тут что-то налипло.
The ending *-oh₁ has been preserved in Lithuanian and Vedic Sanskrit (Classical Sanskrit ending -eṇa is taken from pronominal paradigm; cf. téna, instrumental singular of तद् (tád, “it; that”)).Instrumental plural: PIE ending *-ōys results from the contraction of the thematic vowel -o- and the instrumental case ending *-oys. It has been regularly reflected in all the languages