XPS 7590 computer useless when charging from USB-C and battery level is LOW

I have tons of issues related to USB-C and WD19TB dock station. First of all after few months my laptop stopped charging and Dell replaced motherboard. Then after some time I realized that when I use my laptop on battery and then connect it do dock it's not possible to use it as laptop slow down CPU to minimum. When battery is charged it's starts working normally. If I disconnect laptop from dock and connect to regular charger everything works fine. If I use laptop without charger also everything works normally.  It also do not help connecting charger when laptop is connected to dock, so in general outcome is that if I discharge my battery I'm not able to use dock.  I contacted DELL and they replaced motherboard and dock station but this doesn't solve problem, what is worse they replaced motherboard to faulty one with USB-C port that works only one way and dock with noisy cooler. Then after next replacement they put into my laptop motherboard with completely faulty USB-C port and at the end tech guy put back previous one. Now I asked them for complete replacement of my computer as I do not have time for this experiment where DELL is putting some refurbish parts with quality issues. They rejected computer replacement and want to replace motherboard fifth time. So two questions here:

- first of all is it standard way how DELL treat customers with premium support or maybe I do not have luck in Poland ? 
- anyone with the same issue that computer is so slow when battery is charging and connected to WD19TB that it is not possible to use it ? (BIOS shows 130W charger when connected vi USB-C)