Every reasonably experienced handyman confirmed that the pump can easily handle the incline. However, the water can’t flow through the miner quickly enough, especially because it has to move from the silicone hose into an even thinner, rigid tube. As a result, the water was backing up on the way from the pump into the miner.
The solution is simple: reduce the water flow slightly. I hadn't dared to do this because the manual only showed a picture of it fully open, and I believed that changing the setting might ruin the pump—but I have since found out that is exactly what the regulator is for! 😅
