I know the “render device lost” bug has been making a comeback with the new nvidia RTX series graphics cards. I recently upgraded to an RTX 2070 and started to experience the the issue as well. Many threads say that overclocked cards is the cause as Overwatch is very sensitive to instability. I have attempted to underclock my MSI RTX 2070 Duke 8G OC back to stock values with no avail.
However, I then tried underclocking the memory instead of the core clock and it seems to have fixed the problem for now, or at least it hasn’t crashed within 2 games like it used to. I tested further and tried raising the memory clock back up and it began to crash as it used to. Lowering the clock once again gave me stable games.
My only explanation is that the transition to GDDR6 memory in the RTX cards must not be playing well with some part of the Overwatch code.
tl;dr: Those experiencing the “render device lost” crash with RTX cards should try underclocking the graphics memory to the lowest possible value.