Solved.
Overlay partition is plain.

su
cryptsetup plainOpen --cipher aes /dev/sdb2 enc
<enter your password>
mount /dev/mapper/enc /media/sdb2
<copy data>
umount /media/sdb2
cryptsetup close enc

Partition has been fixed by simple removing the large file. It was an image who was accidently saved into home.
However USB has been recreated