Issue with RT on at 4K ultra with a 4080 super

As above, shown in videos attached.

https://reddit.com/link/1gpu7uh/video/3ou86xsi2j0e1/player

https://reddit.com/link/1gpu7uh/video/an5eirsi2j0e1/player

Would really like a fix to this. My monitor (Gigabyte M28U) which was initially set to 144Hz was manually reduced to 75Hz in display settings cos gaming at 4K ultra with 4080 Super (RT on, DLSS off) results in 60-80 fps - unfortunately the problem persists.