/usr/lib/x86_64-linux-gnu/libmrpt-nav.so.1.5 is in libmrpt-nav1.5 1:1.5.5-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libmrpt-nav.so.1.5.5
/usr/lib/x86_64-linux-gnu/libmrpt-nav.so.1.5.5