U2413, GTX 970, shuts off

I have the exact same problem with my Dell U2413. It is just 26 months old as of 4/Jun/2018.  It started happening 2 weeks prior to that date. I think it is an issue with this model because I'm running it as part of a dual monitor setup and the 11 year old Dell 2007WFP is fine. Both are connected to the same graphics card (NVIDIA GTX 970) in a very high spec Chillblast photo editing computer. I have 2 other Dell monitors over 10 years old and they are still working very well (both connected to Dell computers BTW).