The code in pimport.module (line 1131) does not work properly under either one of two conditions
1) If one value of the allowed list does not have the (optional) label, since preg_match always expects to find a '|'
2) If the key or the label contains the character '\', which will match the initial '\' in the pattern

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crikeymiles’s picture

crikeymiles commented

It also doesn't like it if you set the "Widget" to "Select List" for some reason.

Leaving the widget as "Text Field" fixes this issue.