Glyphs-unprintable characters in the hour part of bar's Date-Time module

[petsam]

This issue sometimes happens and sometimes not and that is the disturbing thing.
At first I thought it had to do with the Greek language, as is set in system, or the selected font. I tried changing those, but the issue was still happening sometimes.

I have run out of ideas about where is this coming from.

My info:

local/lightdm 1:1.30.0-4
local/lightdm-gtk-greeter 1:2.0.8-1
local/lightdm-gtk-greeter-settings 1.2.2-7

Distro: Arch Linux
Kernel: 5.16.2-arch1-1 x86_64
CPU model: Intel Core i3 560
Graphics:
  Device-1: Intel Core Processor Integrated Graphics vendor: ASUSTeK
    driver: i915 v: kernel bus-ID: 00:02.0 chip-ID: 8086:0042 class-ID: 0300
  Device-2: NVIDIA GF116 [GeForce GTX 550 Ti] vendor: eVga.com.
    driver: nouveau v: kernel bus-ID: 01:00.0 chip-ID: 10de:1244 class-ID: 0300
  Device-3: Microdia Camera type: USB driver: snd-usb-audio,uvcvideo
    bus-ID: 2-1.4:3 chip-ID: 0c45:6340 class-ID: 0102
  Display: x11 server: X.Org 1.21.1.3 compositor: picom v: git-dac85
    driver: loaded: intel,nouveau unloaded: modesetting,vesa
    alternate: fbdev,nv display-ID: :0 screens: 1
  Screen-1: 0 s-res: 3600x1080 s-dpi: 96 s-size: 950x285mm (37.4x11.2")
    s-diag: 992mm (39")
  Monitor-1: HDMI1 res: 1680x1050 hz: 60 dpi: 267 size: 160x90mm (6.3x3.5")
    diag: 184mm (7.2")
  Monitor-2: VGA1 res: 1920x1080 hz: 60 dpi: 92
    size: 530x300mm (20.9x11.8") diag: 609mm (24")
  OpenGL: renderer: llvmpipe (LLVM 13.0.0 128 bits) v: 4.5 Mesa 21.3.4
    direct render: Yes

===============================================
$ localectl
   System Locale: LANG=el_GR.UTF-8
       VC Keymap: us
VC Toggle Keymap: gr
      X11 Layout: us,gr
       X11 Model: pc105
     X11 Variant: ,
     X11 Options: grp:alt_shift_toggle

===============================================
## /etc/lightdm/lightdm.conf
[LightDM]
run-directory=/run/lightdm

[Seat:*]
session-wrapper=/etc/lightdm/Xsession
greeter-setup-script=/etc/X11/xorg.conf.d/dm-multihead.sh

===============================================
## /etc/lightdm/lightdm-gtk-greeter.conf
[greeter]
theme-name = Adwaita-dark
icon-theme-name = gnome
font-name = FreeSans 13
xft-antialias = true
xft-dpi = 96
xft-rgba = rgb
xft-hintstyle = hintmedium
background = /home/common/backgrounds/cosmos/comet.jpg
clock-format = %A, %d %B %G, %H:%M
indicators = ~session;~host;~spacer;~clock;~spacer;~a11y;~language;~layout;~power
position = 10%,start -30%,end
keyboard = onboard
user-background = false

[monitor: VGA1]
background = /home/common/backgrounds/cosmos/galaxy-ngc3370.jpg
user-background = false

[monitor: HDMI1]
background = /home/common/backgrounds/linuxmint-serena/dmarcu_romania.jpg
user-background = false