Libs check - lsof non-zero exit code

Hi,

Recently installed xymon-client on a bunch of Ubuntu 18.04.3 LTS and
after fixing the sudoers permissions I'm still left with a red libs
check on all of them.

Error is:
Wed Sep 18 17:50:18 2019 - libs NOT ok
/usr/bin/lsof -n -FpcLfn0 returned with non-zero exit code: 1

xymon-client package is version: 4.3.28-3build1

Any hints where to debug why the systems can't lsof properly?

Thanks

Steve