are you changing the speed from the printer or cura ?

Judging by all the issues we've been getting on here about cura recently.
I'd seriously consider a different slicer.
Slic3r is pretty good. Pronterface with slic3r is better.
There's a few more to look at here: https://all3dp.com/1/best-3d-slicer-...re-3d-printer/