OpenVPN - client connect at boot fails with "Device busy"

[zeroflow]

Hi,

I'm having issues with my OpenVPN clients on my pfSense box. At the moment, I have two clients configured, one to my vServer and one to NordVPN. If I reboot the system, both clients show status up and all statistics look normal except that the gateways are marked as down and no traffic is passing. Now for diagnosis purposes, I've disabled my vServer VPN to narrow the problems down.

You can see the log snippets here: https://gist.github.com/zeroflow/d4570d5f192074af1807d36c1525507e

When comparing both snippets, only one line stands out from the explainable differences (boot logging messages vs reconnect):

ioctl(TUNSIFMODE): Device busy (errno=16)

In addition, the following lines are printed twice instead of once in reconnect.log:

MANAGEMENT: Client disconnected
MANAGEMENT: CMD 'status 2'
MANAGEMENT: CMD 'state 1'
MANAGEMENT: Client connected from /var/etc/openvpn/client2/sock

Looking at the full logs, the same Device busy error message is also printed for the vServer VPN client if enabled at boot.

Sadly, searches for Device busy did not yield any solutions for this problem, so does anyone here have ideas where to start fixing this issue?