is the abbreviated term or short for the word demons. Demons, or personal demons, can be used for someone's ongoing problems they face. It can be the result of anything that is negative. It can also apply to things; malfunctions of equipment, and items not functioning to it's normal use.
Someone who suffers from alcoholism, drug addiction, gambling addictions, would all be examples of DEMS.
"I have mad gambling dems because i spent all of my life's savings away."
DEMS in relation to things:
"My car's engine light keeps turning on, and my brakes suddenly aren't working," would suggest someone has car dems.