Solve Bug?

[Phunkee]

Hello to everyone,

I found some time ago an interesting Polynomial on another forum.
It seems to be a bug in the Prime CAS.
Yesterday I updated my HP prime and tested it again to find the roots of it.
On all other calculators I have, like the HP 48 (withe Erable), the 49g, the 50g
there is the same solution, only the prime seems to be a little more creative ;-)

So I like to ask you if you know what the problem is in this case....

Try to find the root of
f(x)= x^4 - 3x^3 - 2.75x^2 + 12x - 5

It doesn't matter if I do it with solve, zeros... exact or approx mode...I always get the answer
2.5 2. -2. 0


0 can't be a root of this polynomial.
The right solution should be
0.5 2.5 2. -2.

Interestingly, when i try it with proot and type -11/4 instead of -2.75 it works.
solve with -11/4 works too.

My HP Prime is on the newest firmware.
So is there anybody who can explain this behavior?
Thank you all in advance!

Best regards
Oliver