I put new batteries in my OM40 yesterday and today whilst out and about it has been fine. I have been shooting with it set to Auto with TMX3200 rated at 1600. Typically my exposures have been 1.8/2.8 @between 30-250th. All fine.

This evening indoors I was having a play around and set up to take a shot in with fairly low light and was showing f1.8 @ 1/30th. I fire the shutter and it sticks open along with the mirror. Resetting with check on the dial releases it all. I try again and the same.

I have been playing around for some time with this now and what I have found is in manual mode there are no issues. In Auto and Program things play up. It occurs at speeds of around 30/60th and under.

Any ideas why this may only occur in the Auto and Program modes?