I have a Dell U2415 monitor that I've been having issues with for months.  Initially, the set up was 2 U2415 monitors hooked up to a HP Prodesk 600.  The problem started with a solid black line across the bottom of Monitor 1.  Monitor 2 has NEVER had any issues.  First, we swapped monitor 1 with a neighboring monitor that was being used.  Monitor 1 did not experience any issue, however, the monitor from the neighbor did.  We, of course, swapped all cabling with no resolution.  We increased ram in the PC with no resolution.  We changed the monitor refresh rate.  We then swapped the HP with a Dell OptiPlex 5040 with no resolution.  We believe we have it narrowed down to the issue starting when the user is utilizing Gmail or a web-based program.  The user is against using Firefox or another platform and we have already uninstalled and reinstalled google.  Curious to see others thoughts on what the actual issue could be.

Thank You!