I thought when I removed the oil filter LAST time and the smaller rubber annulus seal was left behind in the housing that it was a 'one-off'. However, today I changed it again ( several months on ) and the small rubber annulus seal had partly come out of the filter and the larger, outside, rubber annulus seal came off as well.

No abnormality in the engine was noticed.

I stress that genuine filters were used on both occasions.

Anyone else noticed this? Any ideas why?

Photos attached

You lubed the seal before tightening I assume.

As long as the seals look like they were seated correctly i.e. not kinked, cut or leaking, it's okay.  

Yes, I always lubricate rubber/neoprene seals to save tearing or 'unsealing'. Still puzzled.