Question about TP-Link Deco X50 (3-pack)

I have the simplest possible mesh variant in operation: 2 TP-Link Deco X50, both connected to the LAN. Result: the mesh is extremely unreliable. The slave transmitter sometimes works, but then keeps flashing red and has no Internet. The two boxes are on different floors. But the LAN connection should ensure that it works even without constant wireless contact. I suspect that the "AI Driven" feature from TP Link wants to be too intelligent here and produces errors - with a few if-then-else statements you could probably build a stable mesh. Hence the following questions: - is there anyone for whom the app works ? It doesn't help me much, it also shows OK when the device flashes red. - Is there any way to switch off the AI stuff so that it just does a WLAN without "intelligence"? - does Digitec have a mesh system that works stably?