Comment 6 for bug 1542699

I'm seeing the same issue. What appears to be happening is that there are multiple outputs with the same name, but with different properties. After breaking in gsd_rr_config_match at the end of gsd_rr_config_load_current:

(gdb) p c1->priv->outputs[9]->priv->name
$54 = 0x1b3b370 "DP-3"
(gdb) p c1->priv->outputs[3]->priv->name
$55 = 0x1b3b2f0 "DP-3"
(gdb) p c1->priv->outputs[9]->priv->product
$56 = 0
(gdb) p c1->priv->outputs[3]->priv->product
$57 = 41150
(gdb) p c1->priv->outputs[3]->priv->vendor
$58 = "DEL"
(gdb) p c1->priv->outputs[9]->priv->vendor
$59 = "\000\000\000"
(gdb) p c1->priv->outputs[9]->priv->serial
$60 = 0
(gdb) p c1->priv->outputs[3]->priv->serial
$61 = 808666700

I assume these duplicates come from XRRGetScreenResources, which means it might be a driver issue.

Are you using the NVIDIA binary driver by any chance? (I am)