xfce4 reverts to mirrored dislays

[Per olof Ljungmark]

FreeBSD 11.1-STABLE #0 r326044
nvidia-driver-384.98
xfce4-settings-4.12.1

File
.config/xfce4/xfconf/xfce-perchannel-xml/displays.xml

Problem

I use a dual monitor setup with "<property name="X" type="int"
value="1920"/>", ie. with the second monitor 1920px to the right

On every monitor power down, xfce4 decides that they are mirrored
instead and changes the file displays.xml to value="0" for the right
monitor and the file is overwritten.

Tried

- Setting ownership to the above file to root
- Set the propery <channel name="displays" version="1.0"> to "locked"
- Applied this patch to xfce4-settings-4.12.1:
https://bugzilla.xfce.org/show_bug.cgi?id=14096
https://git.xfce.org/xfce/xfce4-settings/commit?id=e128126f5e32c1018854403bb846cb9d6a091bb0
- "metamodes" "DP-2: nvidia-auto-select +0+0, DP-3: nvidia-auto-select
+1920+0" in xorg.conf (ignored by xfce apparently)
- nvidia-settings
- nvidia-xconfig

.xinitrc has just "/usr/local/bin/startxfce4"

None of the above changes the behaviour and I am out of ideas how to fix.

Are there other files I am unaware of that could override displays.xml?

Thankful for any hints on the subject...