The bug is not locale specific and occurs when the field name contains special character:
Special characters that do work are german umlauts, comma, dot and space.
Special characters that do not work are parenthesis (i.e. “(” and “)”)!
EDIT Sorry, not sure what is going on. Parens seem also to work on my test-instance.
We fail to reproduce the bug in a fresh test-instance, running on the same commit as @blaisorblade’s instance that keeps showing the problem.