wrong result using simplify()

[Adiwa]

Hello forum

I'm playing around with my new HP Prime G2.
Trying to duplicate the inputs of a you tube video I entered in CAS: simplify(x+x+2y+x-y-x)

I got as result x+x+2.*y-y-x (with this strange decimal behind the 2), there's no simplification!
The guy in the video gets perfectly 2*x+y as expected.

What I'm doing wrong, whats going on?

In addition I did several complex things on it as areas between graphs and everything seems to be working fine there.

Any ideas out there - thanks very much.
Adrian