Replace accented characters feature - a couple of issues - what am I doing wrong

Hi all,

Replace accented characters is a godsend for some work I'm doing in Vietnamese, which has a bunch of diacriticals for tone as well as pronunciation. However, some of the replacements aren't working quite right - for example,

Tinh Bình DươngBàu Bàng

becomes

Tinh Binh DuongBaau Baang

where the a's show up duplicated.

Any thoughts why this may be happening? My substitution list for a is:

áàâäãåǻăāąấấặắầầậạẩả

And I was building it up from the default a substitutes, copying and pasting specific unmatched a-characters in the list as I went along.