Is it der, die or das Schlamperei? – die Schlamperei, plural die Schlampereien

Why is it die Schlamperei?

Schlamperei ends in -ei, and almost all nouns ending in -ei are feminine: in a German dictionary, 91% of them take die.

Sense 1

die

[1] colloquial, general: lack of order

[1] umgangssprachlich, allgemein: mangelnde Ordnung

[2] colloquially, regarding the work: sloppy, too little careful work

[2] umgangssprachlich, die Arbeit betreffend: schlampige, zu wenig sorgfältige Arbeit

[1] The apartment gave the impression of a single sloppiness
[1] Die Wohnung machte den Eindruck einer einzigen Schlamperei.

[2] The repair is not paid due to sloppiness
[2] Die Reparatur wird wegen Schlamperei nicht bezahlt.

More source examples (1)

These dictionary examples can include historical and less common uses.

[2] "Madam did not tolerate a sloppiness with her girls" "
[2] „Madam duldete keine Schlamperei bei ihren Mädchen.“