inexplicabale fault in CAS Mode

[Martin Ünal]

Hello everyone,
since I come from Germany, my English isn't perfect. Sorry for that!
I just encountered the following Problem:
I wanted the HP Prime to calculate the roots (is it the right english word? the values of x_0 for which f(x_0) = 0) of
f(x) = x^4 - 3x^3 - 2.75x² + 12x - 5
which are 2.5, -2, 2, and 0.5.
In the CAS mode, I entered
zeros(x^4 - 3x^3 - 2.75x² + 12x - 5)
an got the Output
[2.5 2. -2. 0]
0 is obviously not a root of this polynomial.
Where is the mistake? On my side (and which one?) or on the HP Prime's side (and can it be fixed?)?
I would like to tell you my HP Prime's software version but I don't know how to find it out. Can someone tell me?
I have the same problem when I use the HP Prime Virtual Calculator on my Computer (the 2016_08_29 version).
Thank you for your answers!
Martin