My laptop is connected to 2 external monitors. Soon after screen is locked (xscreensaver), the monitors go into suspend mode.
As of 4.4.x updates, this causes window manager (xfwm4-4.12.3-2.fc23.x86_64) to detect one of the monitors as "disconnected" and all windows are moved to the primary monitor.

When unlocked, both monitors are displaying everything, but windows had been moved already and don't snap back to the 2nd monitor.

Also tried on 4.4.2-301.fc23.x86_64

Issue was not present on 4.3.x and earlier kernels (same setup, booted to 4.3.5-300.fc23.x86_64 does not have the problem)


Note, probably irrelevant, but video hardware is dual:

00:02.0 VGA compatible controller [0300]: Intel Corporation 4th Gen Core Processor Integrated Graphics Controller [8086:0416] (rev 06) (prog-if 00 [VGA controller])
	Subsystem: CLEVO/KAPOK Computer Device [1558:5281]
	Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx+
	Status: Cap+ 66MHz- UDF- FastB2B+ ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
	Latency: 0
	Interrupt: pin A routed to IRQ 35
	Region 0: Memory at f7400000 (64-bit, non-prefetchable) [size=4M]
	Region 2: Memory at d0000000 (64-bit, prefetchable) [size=256M]
	Region 4: I/O ports at f000 [size=64]
	Expansion ROM at <unassigned> [disabled]
	Capabilities: [90] MSI: Enable+ Count=1/1 Maskable- 64bit-
		Address: fee00018  Data: 0000
	Capabilities: [d0] Power Management version 2
		Flags: PMEClk- DSI+ D1- D2- AuxCurrent=0mA PME(D0-,D1-,D2-,D3hot-,D3cold-)
		Status: D0 NoSoftRst- PME-Enable- DSel=0 DScale=0 PME-
	Capabilities: [a4] PCI Advanced Features
		AFCap: TP+ FLR+
		AFCtrl: FLR-
		AFStatus: TP-
	Kernel driver in use: i915
	Kernel modules: i915


01:00.0 VGA compatible controller [0300]: NVIDIA Corporation GK104M [GeForce GTX 870M] [10de:1199] (rev ff) (prog-if ff)
	!!! Unknown header type 7f
	Kernel modules: nouveau, nvidia


Using bumblebee to enable nvidia card when necessary; usually it's left disabled.