Hi, I do not have that experience. I have to say, I do not unpower the gateway that much but when I do, it never fails to connect to Wifi.
If you look in the original Motion Blinds app at the gateway, you see a wifi strength symbol. Is that strong, or is it low? I can imagine that the gateway will go into setup mode if it isn’t able to successfully connect to Wifi. If it would not then you would be stuck, which is worse. Is it possible to put the gateway in a place that has better Wifi? the radio signal towards the curtains can also be checked and the range on that is pretty good, so you could experiment with other gateway locations.
Also, is there much interference in the 2.4Ghz wifi band in your place, and have you ever tried switching bands to find something that doe not interfere too much with neighbors or your Zigbee mesh? I admit I rarely check because most devices connect with the 5Ghz nowadays, and 2.4Ghz is notoriously bad on some channels where I live.
As to the product support: @TedTolboom is right in that Robbshop supports both me and their customers in ways that Hornbach never could/will. So it depends on how you value that support and are willing to contribute to that.
Edit: another thought: how do you unpower the gateway? Do you pull it out of the USB adapter or do you unpower the USB adapter itself? I usually unplug the gateway from the adapter. If you pull the plug on the adapter with the gateway in it, and plug in in the same way, the power may not disappear/reappear as gracefully depending on the quality of the adapter. It may be that this causes the gateway to power up/down badly. Using a different adapter may yield different results if that is the case.