Acer X34 (first 2015 model) displays crawling black lines on previously working overclock settings

Hi all,

New to the forums and I am having a problem (finally?) with my monitor. For some reason my monitor will display crawling black lines that start at the bottom of the screen and continue upwards when the screen is at 100 hz. This refresh rate has previously worked without hiccup since I got it. Weirdly the monitor will sometimes work at 95hz or sometimes 90hz and after a while turning it back to 100hz will sometimes work again. Basically it's a crapshoot. 

I've tried the powering cycling method, changing up the display port cable to a better one, and switched the connection to a different DP on my GPU all to no avail. It is the monitor for certain as I've run the GPU with my TV without the same problem. As I am writing this my refresh was previously 90hz and I changed it to 100 and it works without visual distortion again. Usually when I shut down my computer and restart it, the display will have the black lines and I will have to change to a lower refresh rate. After some time I am able to change it back (though it works randomly) to 100. 

Just wondering if anyone has come across this problem and found a solution or if my monitor is likely on the fritz. 

Thanks