Icons not locked after every reboot although option to lock is/was set

[dr]

The icons are becoming unlocked after every restart (the "lock icons" option seems to deactivate after reboot).
I would like to have the lock enabled to prevent inadvertent removal of symbols.

- no output of "plank -d"
- v 0.11.1
- Linux Mint 18.3 Cinnamon (Kernel 4.13.0-36-generic)
- mutter (I guess for Mint Cinnamon...)

- [ 4.687]
X.Org X Server 1.18.4
Release Date: 2016-07-19
- i7-7500, Intel Graphics, Geforce 940MX (Asus UX3410UQ)

- plank was installed via Mint package application ("Anwendungsverwaltung")

[Dani (damufo)]

Same problem on Debian 9 - 64 bits with XFCE desktop.
Plank installed from apt-get version 0.11.3-2.
Any solution?

Thanks.

[Jaguarandine (jaguarandia)]

I have the same problem. Using Ubuntu Mate 18.04. The Pantheon theme.

[Rich Dell (thedells2)]

It's 2020 and I have the same problem, icons unlock on every restart. I would change docks, but I like this one.