Hi, I'm kind of new to guitar, i've been playing like 6 months and I noticed that with my guitar, sometimes I'll be playing a quick bar cord note, for example on 3rd fret, and Since it is a quick note (eighth note) I have to release my hand so it will stop the sound, right?

But 50% of the time when I do this, I get an accidental artificial harmonic.
If you can't understand what I'm saying, I accidentally get a harmonic when I try to take my hand off of a bar cord note. I know I must be doing something wrong, or does it just take practice in preventing it? Advice please, thanks.

*Edit* By the way I do have a crappy guitar, literally a no- name brand and it's not worth figuring out what kind. Not sure if this has any effect, but just thought I'd mention it.
It shouldn't have anything to do with the guitar, you just gotta practice so you don't do it.
If you keep your pick hand resting on the unused strings like i do (to get better control) then you can just cut the string off with your palm. Thats what i do anyways.
sounds like you need to release more gradually. I used to have the same problem but i fixed it naturally over time without intentionally trying. One day i just watched my fretting hand and picking and noticed all the different ways I mute and release etc.
Schecter C-1 XXX (with SD Dave Mustaine Livewire Actives)
Roland Cube 60
I'm no expert, so this is only an educated guess, but are you letting your hand lightly float above the strings? if so, the string might be touching your hand very lightly, which could be producing the harmonic. I would suggest either muting with your strumming hand, or taking your hand completely off of the strings after strumming the chord. hope this helps
A release is just that....take all pressure off the FRET. This takes practice, that's all.