I've had one cable fail, and one dock fail. I now own three thunderbolt cables, and two working docks, and a dead one.
Personal laptop has 3 USB-C ports, only one of which is Thunderbolt. If I forget and use the more conveniently placed USB-C port, the resolution is limited. If I neglect to connect it to power first, it won't reliably connect to the dock.
Work laptop will connect, but will always decide I want 1080P, I have to manually adjust the resolution each time. I have noticed if the monitor is set to 120 HZ, the laptop refuses to acknowledge it exists. 240 or 60 HZ works.
SO's laptop was quite the quest. It works now, but originally it refused to activate the display. Other ports on the dock worked, the display itself worked with a single DisplayPort -> Thunderbolt cable. The display was listed in the graphics card driver software when connected via the dock, it just refused to allow me to enable it. Things would work without a display driver, or a really old version of the driver. Various driver removal utilities didn't help. I flattened the laptop and installed the latest drivers. Things work for now.
I've come away from this mess with a setup that mostly works, but surely doesn't feel stable. And if it stops working, I have basically no clue as to why. Could be a failed part, could be a driver issue, nothing really gives me any feedback as to why it's not working.