VFP parser mistakenly recognizes && inside a string literal as begining of the inline comment. You can split string literal so there's no && for parser to find.

? strtran("change &" + "& to something", "&", "a")

>? strtran("change && to something", "&", "a")
>
>fails with "command contains unrecognized phrase/keyword".
>
>Why?
>
>--rab