vbox VBoxClient: DND: Failed to connect to the VirtualBox kernel service, rc=VERR_ACCESS_DENIED

[usakhncit]

Hi
I have installed FreeBSD-12.2 in VirtualBox, along with virtualbox-ose-additions. Whenever I login to XFCE (or MATE) Desktop, the following error appears in Notification:

VBoxClient: DND: Failed to connect to the VirtualBox kernel service, rc=VERR_ACCESS_DENIED

So, I looked in "Startup Applications", and found following script/app:

Name: vboxclient
Command: /usr/local/bin/VBoxClient-all
Comment: VirtualBox user session services

I tried to execute this command (/usr/local/bin/VBoxClient-all) manually in Terminal, and it produced the above mentioned error again. Then, I tried to execute this command (/usr/local/bin/VBoxClient-all) as super-user, but produced following error:

/usr/local/bin/VBoxClient-all: /usr/bin/VBoxClient: not found

Although, it seems that the error is not practically affecting my system, as I can access shared directory and can copy-paste text between Host (Linux) and Guest (FreeBSD), however, I have two options here:
1. Remove it from "Startup Applications"
2. Try to fix it and learn something in the process
So, I took the 2nd route and started trying to fix it
First I confirmed that the virtualbox-ose-additions are still installed and upgraded to the latest version.
Second, I confirmed that VirtualBox services are mentioned in my /etc/rc.conf as:

vboxguest_enable="YES"
vboxservice_enable="YES"
vboxservice_flags="--disable-timesync"

Third, I created a soft-link (/usr/bin/VBoxClient) pointing towards (/usr/local/bin/VBoxClient-all). However, I am still getting the same "ACCESS_DENIED" error as normal user. But when I try to run it is super-user, the Terminal shows no output and the system becomes unresponsive, until I press Ctrl-C to abort. It shows that it may not be the proper way to fix this issue.
Now I am out of ideas and looking for your advice to fix it.
Thanks