Rear hatch problem

2011 Toyota Highlander rear hatch opens then immediately starts to close but it chatters all the way down. If you hold the door open then it will slam down. Tried all suggestions with resetting it( glass door opened and closed, reset glove box button) started all of a sudden, is not sporadic does it every time. Is it the gas struts,motor . Everything appears to be attached. Any suggestions appreciated. Car has 184,000 miles, otherwise in great condition
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