If the monitor keeps disconnecting and reconnecting or flashing through the hub/dock's DP port, the issue may be caused by the connected laptop, DP cable, monitor, or hub/dock itself.
Here are some troubleshooting tips that may help you locate and resolve the problem.

For laptops:

Try the device with a different laptop with a USB-C port, and ensure that the C-port supports DP Alt Mode (display output) to see whether you can get a stable connection.

For DP cables:

Verify that all devices are securely attached. Try the device with a different DP cable. If possible, plug your DP cable directly into your devices and see if you get a stable connection.

For monitors:

Try the device with a different monitor.

For hubs/docks:

Confirm whether the LED light is on when connected to a laptop. Try with a different hub/adapter to see whether you can get a display for your laptop.