/usr/lib/x86_64-linux-gnu/libplb.so.1 is in libplb1 1.5~r1+repack1-3.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libplb.so.1.5.1
/usr/lib/x86_64-linux-gnu/libplb.so.1.5.1