Pebbles, stones, gravel, etc. in washer pump filter

[userP2s5NP4pk6]

Model WF330ANW XAA 02

I keep finding a good amount of large residue in the pump filter.
Where does this come from and how to fix the issue?

PS: I've read the thread "Why is there dirt in the bottom in my machine?" and the solution offered there does not seem to apply to my problem.

Coin for scale

[userP2s5NP4pk6]

It turns out the issue has nothing to do with the washer.
It is because the drain pipe was not properly installed.

So if you do buy a new washer, make sure to fix your drain pipe first or you'll get into the same problem.