Octave on a string violin 3/4

Q: I have a 3/4 violin and when I play an open a string I get the octave above also.

Things I have done:
I have new strings on the violin (red label)
varied the amount of rosin on bow.
varied bow tension.
varied the bow pressure on the string.
use no mute or attachments.
physically violin in good condition
stable condition (soundpost, bridge,fingerboard,pegs, nut etc).

I would appreciate any insight in the cause of this problem

Much thanks,
Robert

A: Look very closely at the string path. The string contacting the
fingerboard, or position marker tapes, as it vibrates could cause the stated
symptom.

It is also possible that when the A is played you are getting a
sympathetic vibration from the part of a string between the bridge and the
tailpiece. You need to get someone else to play the violin while you look
closely and poke around with your finger until the octave stops sounding.
If this is the problem, tighten or loosen the tailgut, slip the bridge
forward or back, anything to slightly change the vibrating length of the
offender.

Also check the nut grooves. The contact point, the point from which
the string vibrates, should be at the fingerboard end. If the contact point
is half way up the slot the string will at least be muted and it might be
able to force a harmonic.

Lastly, the new string might be from the same batch as the previous
string. They could both be bad. Red Label strings are the heaviest,
nastiest strings you can buy. Maybe try a D'Addario Prelude; still a cheap
steel string, but a much better one. To upgrade the A string further you
would need to get E, D, and G strings to match.

I can't see how the problem could be caused by your bow.

Steve Mason