I have two of these PB278 monitors and they are definitely old at probably 5-10 years, but the more annoying thing is that the oldest doesn't seem to autodetect inputs very well. You actually have to reboot the Mac in order for the display to get recognized. I sure remember those bad old days when that was true.
The symptom is that if you unplug the display and replug it in, the input is not recognized. Happens on DisplayPort and with a wide variety of USB C hubs from Satechi and others at least on my MacBook Pro 2017.
It's strange that it doesn't seem to happen on other monitors, and it might be an issue with the 2017. Overall, getting these things to work is a little hard, my other PB278 normally does synchronize, but sometimes it just seems to forget how to see an input 🙂