Q: macOS Sierra intermittently only detects 2nd display as 800x600 when reconnecting
At work, I've been using a mid 2014 MacBook Pro Retina 15-inch connected to two Thunderbolt Displays. The one of Thunderbolt Displays is daisy chained to the other via thunderbolt, and I then connect to with thunderbolt.
Normally throughout my day I'm disconnecting and using my laptop away from my desk, but when I return to my desk, I usually use my MBP with the lid closed and just use the two Thunderbolt Displays.
Despite this setup historically working just fine, after an up grade to macOS Sierra 10.12 I've hit an issue when my laptop wakes up after being reconnected to the Thunderbolt Displays.
One display will initialize correctly at 2560x1440 but the other display will only run at 800x600. If I try and manually adjust the resolution settings for the displays, I can only select 800x600 for the effected display.
The MBP has two Thunderbolt ports, and if I switch which port the pair of displays are connected two, the monitor forced to 800x600 swaps. Either way, once the issue starts, I'm stuck with one display at an abnormal low resolution.
If I disconnect the two displays, power cycle them, and plug them back in, I still have the issue.
If I open or close the MBP's lid, the MBP's screen works at normal resolution, but I still have the issue.
The only workaround I've found right now is to reboot my MBP. Then the displays work normally.
So far, this issue seems intermittent, but I've encountered it 4 times this week since upgrading.
Mac Book Pro, Mac OS X (10.5.2)
Posted on Sep 22, 2016 1:05 PM
