If nothing looks more promising, try a different display. I have experienced a problem that resembles yours when I tried to use a modern Dell 4K resolution (8 megapixel) display with my RPi 3. An older display (without 4K capability) works. I have not tried my high resolution display recently, but will conduct an experiment with up-to-date F26 software if there is any interest.
I do not know whether this display sensitivity was present with F25 - other problems made it necessary for me to blacklist VC4 for F25 (and pre-release F26.)