S2417DG, multiple issues

Last night I noticed something weird with my monitor.

1. When I put the computer to sleep mode, the entire monitor screen flashes red, green, and blue solid colors.

2. Sometimes when I turn the monitor on (computer on), the resolution automatically changes to 1024 x 768 and I have to restart my computer to change it back to 2560 x 1440. It happens intermittently but still annoying because when I'm in the middle of doing something at work it throws me off.

3. The 165 HZ OC does not work, I tried setting it many times, tried different DP cables, I tested it in two computers - with an AMD RX 580 and a GTX 1080 Ti and it does not work for both! When I enable 165 HZ the screen goes red and a dell logo appears and it looks like its tripping and the changes were not saved and the 165 HZ option is nowhere to be found.

Please advise.