Very high phase rotations, particularly close in frequency, can get lost in measurements due to smoothing. And so you can’t assume that they are actually there and therefore correctable with filtering. Generally if you find you need 8 x 2nd order all-pass filters, then I’d suggest revisiting your loudspeaker design. It sounds like there are time alignment issues or something else. Guiding you on loudspeaker design is outside the scope of our support. I’d suggest posting your loudspeaker design on other loudspeaker forums and asking for tips on how to optimise it.