False positive symlink loop detection for amdgpu-dkms (lubuntu 18.04)

The console output:

$ debsums -c > debsums.txt
debsums: Error: symlink loop detected in path 'usr/src/amdgpu-18.50-725072/Makefile'. Please file a bug again amdgpu-dkms.
$

The /usr/src is symlinked to /usr/share/.src. '/usr/src/amdgpu-18.50-725072/Makefile' is not a symlink, but a file. The md5sum of this file is ok. amdgpu-dkms package is from amdgpu-pro pack.

I have btrfs filesystem and did some hardlink optimizations by FSlint Janiator.

I don't know what is wrong.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: debsums 2.2.2
ProcVersionSignature: Ubuntu 4.15.0-47.50-generic 4.15.18
Uname: Linux 4.15.0-47-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.6
Architecture: amd64
CurrentDesktop: LXDE
Date: Sat Apr 20 17:25:10 2019
EcryptfsInUse: Yes
InstallationDate: Installed on 2018-06-11 (313 days ago)
InstallationMedia: Lubuntu 18.04 LTS "Bionic Beaver" - Release amd64 (20180426)
PackageArchitecture: all
SourcePackage: debsums
UpgradeStatus: No upgrade log present (probably fresh install)