The Brief: Refers to the frantic state of mind someone might experience when high on meth. "Tweaking" can also be used as a slang term to reference someone's erratic or "crazy" behavior.

DEEP DIVE
Tweaking refers to the frantic and compulsive behaviour someone might experience when high on methamphetamines (meth or crank). Though the effects are different, tweaking is to meth as tripping is to shrooms.
I had this crazy dream about a wedding at my dad's house & my dad was smoking weed and tweaking out on crack and I brought 2 girls and one of them ate every single pair of shoes they had and threw them up in the bathroom
— Adam from Allstate (@adamatkinson180) October 5, 2018
People often use tweaking as slang to explain the reason they might make mistakes. If someone were to do something wrong or make a basic error, they might explain it with, “I guess I’m on drugs” or “I must be tweaking”.
if this weather+sunset at 7:15 doesn’t make u insanely happy, ur tweaking
— pinstripe high waters, I dress like a golfer (@iiames5) March 10, 2019
One might also use “tweaking” to point out if somebody (or something, like Instagram) is “freaking out” or not working.
In this case, one could also call the person freaking out, a “tweaker”.
First time smelling catnip.
He is TWEAKING. pic.twitter.com/KupYV7Yv2Q
— Jordynne Grace (@JordynneGrace) March 14, 2019
*facebook gets to tweaking*
*instagram won’t load*
Wassup Twitter 😭— Alee💰. (@igotsomuch_) March 13, 2019