Normally this is a sign your system is struggling to keep up with the processing demands of the program.
It directly relates to the resolution you are working at within the project. The higher the resolution the more demand on the system. So typically a system that can cope showing a full sized monitor running a 1080 x 720 resolution project may well struggle at using the monitor for a 1920 x 1080 project.
You could try reducing the working resolution of your project until you have finished editing it.That may help.
The screen itself may not be a problem unless it has a different resolution to your other monitor. I personally would not mix different resolution monitors on an editing setup.
You were right about the resolution. I changed monitors a few weeks ago and didn't change the resolution to match the primary one. Now it works correctly, both are now 1920 x 1080. I use a Dell 9020 I5 box