@M-Andre-Z-Eckenrode said: @Coises And just now tried Find (\w)a(\w) and Replace \1z\2 with the same list of words, which definitely resulted in at least one anomalous replacement (average became avevzie), possibly more, but the mistakes are more difficult to spot at a glance in this case. I hate continuing to bother you about this with different questions, but I am so stumped. Have you noticed: Do bad substitutions happen if the document is set as UTF-8, or is it specific to ANSI? (For a test, just use Encoding | Convert to UTF-8 on a document containing your test text before trying to Replace.) Have you ever seen a bad replacement where the replacement string did not use a capturing group reference (like \1 or \2 or $1 or $2)?

@Passant-Delarue , Initial guess: turn off “. matches newline”, otherwise your .* will greedily match the whole file.