I don’t know your barometers but the ones I know do not have mechanism permanently attached to a vacuum box. Levers system is gently pressed onto the box by pre tensioned hair spring or wave shaped spring. It is possible that your barometers are jammed by dirt (spider silk maybe?) or rust in hinges or pivots. Repairing requires precision of a clock maker. Inspect first with good light and strong magnifying glass. Professional help:
http://www.barometerparts.co.uk/pgrepairs.html
Michael
September 2007