SUMMARY
Window titles don't fully refresh when window titles are aligned to the left AND there's no menu to the left icon in titlebar buttons. There are leftovers from the previous name in the beginning.

STEPS TO REPRODUCE
1. Go to System Settings -> Application Style -> Window Decorations
2. Change "Title alignment" in Breeze(Oxygen is affected as well) Theme to "left"
3. Make sure you removed "Menu" item from titlebar buttons as it possibly hides the issue
4. Make any app change its title during runtime, for example Konsole and change directories or System Settings when you go back and forth to/from "All settings" and Global Theme

OBSERVED RESULT
The beginning of the title stays the same. So for example when I'm in console it's like this:
1. I start in ~ and the title is "~ : zsh -- Konsole"
2. I cd into Downloads and the title becomes "~:wnloads : zsh -- Konsole"

EXPECTED RESULT
The whole title should refresh, so in the example above it should be:
"Downloads : zsh --Konsole"

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Arch Linux
KDE Plasma Version: 5.18.5
KDE Frameworks Version: 5.70
Qt Version: 5.14.2

ADDITIONAL INFORMATION
The issue isn't happening or isn't visible when there is "Menu" item in titlebar buttons on the left.
The title refreshes fully when window is resized.
Happens both on Wayland and X11.
Happens also on Manjaro with same data as above except KDE Frameworks which is 5.69