I am now testing with nothing else connected. Both cables for UP2715K #1 are connected to Bus 0. That works fine.
UP2715K #2 is connected one cable to each of the other 2 Thunderbolt buses. It is better than before, so far, but still a little glitchy. 60Hz testing fails. Sometimes there are graphical anomalies, particularly if you move a window from the primary display. The slight progress is encouraging, though.
UP2715K #2 is connected one cable to each of the other 2 Thunderbolt buses. It is better than before, so far, but still a little glitchy. 60Hz testing fails. Sometimes there are graphical anomalies, particularly if you move a window from the primary display. The slight progress is encouraging, though.