Seamless mode "not supported"

[Paul43]

Windows 10 host and Fedora 24 guest. VirtualBox 5.1.4 installed on host and Linux guest additions 5.1.4 r110228 installed on guest. Both machines are updated.

The guest won't boot into seamless mode. The logs show that seamless is "not yet supported". Seamless mode seems to be supported every so often. Any eta on when it'll come back?

00:00:12.085212 VMMDev: Guest Log: VBoxService 5.1.4 r110228 (verbosity: 0) linux.amd64 (Aug 16 2016 19:47:02) release log
00:00:12.085240 VMMDev: Guest Log: 00:00:00.000120 main Log opened 2016-09-07T16:08:24.750918000Z
00:00:12.085279 VMMDev: Guest Log: 00:00:00.000203 main OS Product: Linux
00:00:12.085434 VMMDev: Guest Log: 00:00:00.000354 main OS Release: 4.7.2-201.fc24.x86_64
00:00:12.085481 VMMDev: Guest Log: 00:00:00.000405 main OS Version: #1 SMP Fri Aug 26 15:58:40 UTC 2016
00:00:12.085509 VMMDev: Guest Log: 00:00:00.000433 main Executable: /opt/VBoxGuestAdditions-5.1.4/sbin/VBoxService
00:00:12.085516 VMMDev: Guest Log: 00:00:00.000434 main Process ID: 933
00:00:12.085520 VMMDev: Guest Log: 00:00:00.000435 main Package type: LINUX_64BITS_GENERIC
00:00:12.088348 VMMDev: Guest Log: 00:00:00.003268 main 5.1.4 r110228 started. Verbose level = 0
00:00:12.089083 GUI: UISession::sltAdditionsChange: GA state change event came, notifying listeners.
00:00:12.089097 GUI: UIMachineLogicNormal::sltCheckForRequestedVisualStateType: Requested-state=4, Machine-state=5
00:00:12.089102 GUI: UIMachineLogicNormal::sltCheckForRequestedVisualStateType: Rejecting 'seamless' as is it not yet supported...
00:00:12.090553 GUI: UISession::sltAdditionsChange: GA state really changed, notifying listeners.
00:00:12.090569 GUI: UIMachineViewNormal::adjustGuestScreenSize: Adjust guest-screen size if necessary.
00:00:12.090575 GUI: UISession::sltAdditionsChange: GA state change event came, notifying listeners.
00:00:12.090579 GUI: UIMachineLogicNormal::sltCheckForRequestedVisualStateType: Requested-state=4, Machine-state=5
00:00:12.090583 GUI: UIMachineLogicNormal::sltCheckForRequestedVisualStateType: Rejecting 'seamless' as is it not yet supported...

[mpack]

Moved to "Linux Guests" since the host OS is irrelevant to the question asked.

[Perryg]

You probably need to post a ticket at bugtracker. Not a lot of the power players use seamless and it is a hit or miss target if it will work.

[rhealitycheck]

I'm also seeing this behavior but only in Fedora KDE, when using GNOME seamless works fine. I should mention I have the same specs as OP.