Hey Lodrix,
As previously mentioned, the majority of Rendering Device Lost errors while using the RTX cards were fixed with the driver update.
It’s possible that there are still older drivers on the computer causing a conflict though and if you want to post a new DxDiag we can take another look. If it’s not a driver issue though, then it’s likely a deeper problem with the hardware or a conflict with another program. You can read more about the Rendering Device Lost errors here.