Parkside PHD pressure washer valve ... piston ... thingie?

The base is a bit wider than the the original (worn down) part. I managed to reassemble the pump and the printed parts fit perfectly, but the thin stem where the little ring attaches broke apart in seconds.

I ran a few tests with the part printed as shown in pic, also sideways and angled with same results. Use something else than PETG. 

I may or may not try to redraw the part from scratch at some point.