On Xubuntu 16.04 Kdenlive can not save the Theme / Style information.

I set the style to "Breeze" and the theme to "Breeze dark", I also save this as a layout configuration, however after a restart of Kdenlive the theme is set to a light theme (do not know which one) and the icons are much too big. I have to manually set the style to default and then the icons are small again, then I set again to breeze and then I change the theme to breeze dark. But after restart this settings are forgotten and the GUI shows again with a grey theme and much too big icons and I have to repeat that settings. 

When starting Kdenlive from bash, I get only this output while changing themes (or style):

QXcbConnection: XCB error: 8 (BadMatch), sequence: 41699, resource id: 75498097, major code: 130 (Unknown), minor code: 3

It is really a pain to try to get Kdenlive showing up a clean GUI on a XUbuntu 16.04 system, especially with higher dpi settings (144 dpi e.g.). First I had no icons at all, now I installed some KDE packages and qt5ct which helped a little bit, but it is still not perfect - btw when there are dependencies to other packages, why are they not mentioned in the ppa? 

My first impression would have led to a "not usable, broken GUI, uninstall" conclusion, but I want to help to make Kdenlive better, so I dived in a little bit. 

It would be generally really nice if the developers accepted the real world fact that many people on Linux systems are NOT running KDE as their DE, especially performance-oriented power-users like to avoid a desktop system that starts x processes and does unknown things just to start a program - usually video editing people tend to optimize their system to run the bare minimum to squeeze every CPU cycle out for maximum editing capabilities. 

I understand that QT5 is nice programming environment, and many KDE applications, however, have no problem at all running on a clean XFCE desktop - it would be really nice if Kdenlive would like to behave as a good desktop citizen too and just worked on a clean Xubuntu 16.04 (LTS) after adding the recommended PPA and installing. Thanks!

BTW I feel like the distinction "theme / style" is too differentiated - there are really a lot of things to keep track of with video editing and I am constantly confusing "Theme" with "Style" - it is distracting for a user to have multiple sub-divisions for GUI-related settings - I understand that you might have to obey to the KDE view of the world, but you could put these GUI relevant settings into only one submenu, that would be less confusing. 

I am trying to be constructive and am trying to help to get Kdenlive some better adoption also for pro editors, because I like the potential of the program -  this is why I am taking the time to report here, so I hope it is not perceived as "ranting", thank you!

These very basic GUI things of course must be 100% OK as a first step to even think of letting anyone adopt a different tool into his personal video editing workflow, so please do not underestimate the negative impact a broken GUI has on many users.

Thank you very much for your attention,
have a nice day!