Two problems here: (1) the text of the error message does not appear in its entirety (I tried different zoom levels and full screen to no avail) and (2) the message does not help much to know how to fix the search. What would be better, would be something similar to the "use smart search instead?" clickable message when running a precise search. I realize that the latter is a generic message whereas suggestions for search syntax would be a more complex proposition. Still, fact is that the current "solution" is not that helpful.
This post is not asking how to fix the search below (I already know that). It is making an observation that one has to figure out how to solve the problem with not much to go on in the error message. Sure, there is a red line, which I interpret as indicating where the fix needs to be (though I am not 100% confident of this). The message "missing value for operator" is somewhat cryptic. It turned out that putting the word "repetition" ahead rather than after the parenthesis made the search work, but that it should be so is far from intuitive to start with and certainly not obvious from the error message.