The Chainsmokers' Drew Taggart just can't seem to stop one particular uninvited guest from showing up at his L.A. home -- this time, she falsely claimed she was his WIFE ... TMZ has learned.

Law enforcement sources tell TMZ ... Thursday morning, the woman popped up for the second time in two months at Drew's house, climbing a fence to get onto his property.

We're told the woman then walked up to the front door and rang the bell, while Drew was chilling out inside the house.

Our sources say Drew spotted the woman sitting on steps outside his home and immediately called 911, prompting officers to respond.

When police arrived, they spoke with the woman, who tried to pass herself off as Drew's wife. However, Drew got engaged last year to model Marianne Fonseca announcing it on Instagram.

Another issue is that the uninvited guest may not be all there ... Cop tells us they brought her to a hospital for a mental health evaluation.

You may recall ... this same woman paid a visit to Drew's abode in January while he and Marianne were inside.

A similar situation went down -- the woman went to the front door and stayed outside for a bit before she was cuffed by responding officers and led to a squad car.