Some Ashkenazim are medakdek to pronounce their Aramaic "correctly". And they know that there is a mapik heh in Amein Yehei ShemeiH Rabba. Thus, יְהֵא שְׁמֵ*הּ* רַבָּא מְבָרַךְ לְעָלַם וּלְעָלְמֵי ...
Kitzur Shulchan Aruch (Ganzfried) 67:6 states: "A vow does not take effect unless one's words and one's heart agree. However, if one made a vow by mistake, not intending to say what one did say, ...