Hasselblad H1 film back issue?

My perfect condition H1 has started to act up. I'll load film in it, and it will show 16exp remaining. As I shoot, the number drops correspondingly. Problem is the last two rolls it will show blank, like nothing is in there, when a few minutes earlier it showed a correct setting e.g 6 exp remaining.

I tried to shoot what I thought was the remaining film, but those came out blank when developed.

Any (useful to this situation) ideas? I'll try to clean the contacts but at the moment cannot find any isopropyl alcohol anywhere.

I recommend that you take the film back to Mike at Samys Fairfax to check out. If he has to charge you, the charges will be less than others and without the shipping both ways. He is my go to repair man.

Does the back have a battery to ensure that it remembers where it is on the roll when the body is switched off? If so, the backs are now old enough that the death of that battery is very possible - which could cause the problem you describe.

The backs do have a battery that saves the settings. But when connected to the camera, it gets its juice from the main body.
I shot another roll of film in the 'bad' back with no issues today. Then when I tried to load another roll, it didn't register that there was a roll in it, so it didn't load. I had cleaned all the contacts with isopropyl alcohol.
I took my spare back and loaded that, no issues.

But.. going back to the battery issue - on the main body the battery life showed the last segment remaining. In the manual it states that when the message 'low battery' appears, that is when things stop working.
It seems that that may not be the case. I'm thinking that the batteries (in the camera body) need to be changed at that point.

So thanks for bringing up batteries, I'm hoping this is an obvious fix. And Sirius, thanks for recommending Samys in case I need to make a visit. It's been a while since I've stopped by.