Unable to create webcam files each minute but every30 seconds OK??

I have just started to have a very weird problem …

My daily and hourly movies stopped and when I checked why, I noticed that the webcam images each minute were not being created … this started when I updated to b41 from b39 … in trying to diagnose why I ticked to create every 30 seconds and these 30 second files are created OK but still not the per minute ones … can anyone give me some clues please?