Yes it is an electronic camera and any electronic fault is parts camera but a body only OM10 or OM1 are easy replacements.
Originally Posted by nsurit
if the altering the ISO setting alters the manual exposure then the electronics is ok and the 2nd mirror may have stuck up or partly up.
you could remove the lens and lock the shutter on B.
get a can of Zippo and a cassette tub and large darning needle and drip a droplet of Zippo on hinge then dry fire the camera 50 times on 1/125 then try meter again.
Not Im assuming the mirror has a half silver and mini mirror for the spot like an OM4 too long since I used one.
Don't clean the mirror or play with the hinge of the mini mirror try droplets and excersise lots of times.
if the fault clears don't lube use the camera more frequently.