Strange behaviuor with 2 *.flif images

[herb]

Hello Pierre,

I am working with XnViewMP 1.7.2 and also NConvert 7.182 (private version).
In XnViewMP I use catalog but do not store thumbnails. So thumbnails will be build every time I click on directory.

In my pool of testimages I found 2 *.flif images which show a strange behaviour:
In XnViewMp
- sometimes I do not see a thumbnail (although XnViewMP was running a very long time)
- sometimes I see a thumbnail
- same is valid for preview.
- sometimes I do not see a thumbnail, but I see a preview.
(Exiftool does not say that there is an embedded image, so I think it should be generated by XnViewMP)

I know this sounds crazy. (No I was not drunken doing the tests)

Exiftool displays both files as animation.

Can you tell me what should be the correct behaviour for these 2 images.
Thanks for your help in advance.

Best regards
herb

[xnview]

Yes very strange. I'll check why...