flogs a dead horse (verb) beat a dead horse: dwell on
Sinonime: Gordian knot, Pandora's box, Pandora's box, complex problem,
complexity, complication, difficult situation,
difficulty, dog's breakfast, entanglement, hard nut to crack, headache, hornet's nest, hot water, hot water, mare's nest, mess, predicament,
problem,
quagmire, quandary, snafu, snake pit,
snarl, trouble, troublesome problem, unpredictable situation