broken image decoding in 18.04.1 AppImage

[Harald Albrecht]

My recent project edited in 18.04.1 AppImage looks fine in preview, but 
fails to either render or timeline preview render: aborting with CRC 
errors in image files. Checked the image files, all fine, Kdenlive still 
doesn't render. Rewrote these image files. Nope, still CRC nonsense. 
Sometimes, playing the timeline even crashes Kdenlive.

The same project renders fine in 17.12.0d. Go figure. 18.04.1 is broken. 
Period.

Best regards,
Harald