Mak 4 and 1 1/2" stand pipe question

[DJ88]

1" pipe to the sump, two 90 degree bends

There is the reason right there.

I was running 1.5" all the way to the sump. no 90 degree bends. one 45 and that was it.

In effect you are running a 1" drain. I had a 1.25 restriction(didn't need it) but the entire plumb was 1.5".

hth