I originally suspected the GTX 1050 Ti GPU, but the laptop outputs a perfect image to an external 4K monitor, on the I gpu and gaming using the 1050 to is fine, so I believe the fault is with the screen or display hardware.
Dell XPS 9570 i7-8750H 16GB DDR4 256GB NVMe GTX 1050 Ti 15.6 Laptop 1YR Warranty
Dell XPS 9570 15-inch (2018) | Core i7-8750H | 32GB | Black | 512GB
Laptop CPU GPU Cooling Fan, Low Noise Replaced Cooling Fan for XPS 9570 7590, 5530 5540, with 4 Pin Connector, for DELL XPS Series
Haofy Silent XPS 15 Laptop CPU GPU Cool Fan 4 -PIN Connector Efficient Heat Department for XPS 15 9570 7590 5540 Workers Aluminum ABS Material 2 Parts
Deal4GO Slot 2 2280 M.2 SSD Heatsink Thermal Shield 04TW9C 4TW9C for Dell XPS 15 9500 9510 9520 9530 9570 Precision 5550 5560 5570 5580 Latitude 5500
Deal4GO 2 Pack Laird T-Flex 340 Soft Thermal Pad Gel 70x22x2MM for NGFF M.2 2280 PCIE NVME SSD Heatsink fit for Dell XPS 15 9550 9560 9570 Precision 5510 5520 5530 88DJK 088DJK
