External display keeps going black...help

I have a 2013 Mac Pro (black) and I have connected to it and external Seiki Pro monitor vis DiaplayPort. I've never had any issue's with it except when updating to High Sierra a few months back. I'll be working and suddenly my mouse will freeze which is when the external monitor goes black.

When I disconnect the Thunderbolt cable connected to the MP and reconnect, sometimes that will bring back the external monitor to life, sometimes it won't, unless I do that a few times.

I'm planning on getting another cable today. If the cable doesn't fix the problem, is there anything else I should be looking at?

Thanks in advance!