This is the 13426th most frequent German word.
bemängeln
To criticize or find fault with.
The verb 'bemängeln' is used here in the sense of criticizing or pointing out flaws, generally indicating dissatisfaction.
Er bemängelt immer die Qualität der Arbeit.
He always criticizes the quality of the work.
In this context, 'bemängelten' (past tense of 'bemängeln') conveys a complaint or discontent concerning the delay of the delivery.
Die Kunden bemängelten, dass die Lieferung verspätet war.
The customers criticized that the delivery was delayed.
Here, 'zu bemängeln' serves to indicate the absence of issues or complaints, showing a neutral or positive evaluation.