I just purchased a
mid-2019 MacBook Pro (MacBookPro15,2)
2.4 GHz Intel Core i5
Model A1989, Product Z0WQ
16GB RAM 2133 MHz LPDDR3
Intel Iris Plus Graphics 655 1536 MB
MacOS Mojave 10.14.6, Dark Mode
I too have a similar issue. My flashing/glitch is towards the bottom of the screen like yours but only shows up for 0.5s or less.. and is usually bright magenta or green. I cannot intentionally replicate the issue, it just seems to happen randomly or at least when I have several applications running for school.. ie Word, PowerPoint, Safari (multiple windows each with multiple tabs), iCal, Mail..etc.
From what I have read, the issue might be related to the computer's sleep/awake settings and or the auto dim settings. I haven't had any issue after performing the following steps
1) Reset the SMC https://support.apple.com/en-us/HT201295
2) Reset the NVRAM/PRAM https://support.apple.com/en-us/HT204063
3) Turn off "Automatically adjust brightness" and "True Tone"(System Preferences > Displays > Uncheck these options)
4) Turn off "Night Shift"
5) Turn display off after 15 minutes. (System Preferences > Energy Saver > Battery > Turn display off after 15min)
No idea which one actually solved the issue but hope this helps.