Why Does Retina MacBook Pro (2012) Suddenly Hibernate With Lid Open?

Question

I'd like to know why my Retina MacBook Pro (2012) at certain times suddenly go into Hibernate mode when I'm actively using it with the lid open and what I can do to prevent this.
I know this is hibernate because of what I see in the Console logs and the fact that I can't trigger a wake by using the keyboard/trackpad/mouse.  Only the power button causes it to wake up.
This usually happens when I wake it from sleep and plug it into an external monitor via HDMI to HDMI connection.   The lid is open and I use both displays.    This happens about 30 seconds to a minute after I wake from sleep.  At the time I'm not plugged into the power supply because I believe it's generally a good idea to let the batter drain and the recharge it.  The last time this happened it was about 35% to 40% charged.
Hardware Overview:
  Model Name:    MacBook Pro
  Model Identifier:    MacBookPro10,1
  Processor Name:    Intel Core i7
  Processor Speed:    2.6 GHz
  Number of Processors:    1
  Total Number of Cores:    4
  L2 Cache (per Core):    256 KB
  L3 Cache:    6 MB
  Memory:    8 GB
Software:
OS X Yosemite (all latest updates installed)
{some 3rd party software}
Let me know if you need more information.
For the gory details of what I see in system.log, read on:
This is about the time the hibernate happens.  I've replaced my laptop's name with {COMPUTER NAME}
Mar 20 18:29:26 {COMPUTER NAME} identityservicesd[375]: <IMMacNotificationCenterManager: 0x7f87d510c9e0>: notification observer: com.apple.iChat   notification: __CFNotification 0x7f87d5210a90 {name = _NSDoNotDisturbEnabledNotification}
Mar 20 18:29:26 {COMPUTER NAME} identityservicesd[375]: <IMMacNotificationCenterManager: 0x7f87d510c9e0>:    NC Disabled: NO
Mar 20 18:29:26 {COMPUTER NAME} identityservicesd[375]: <IMMacNotificationCenterManager: 0x7f87d510c9e0>:   DND Enabled: YES
Mar 20 18:29:26 {COMPUTER NAME} identityservicesd[375]: <IMMacNotificationCenterManager: 0x7f87d510c9e0>: Updating enabled: NO   (Topics: (null))
Mar 20 18:29:26 {COMPUTER NAME} WindowServer[218]: device_generate_desktop_screenshot: authw 0x7fba81c2e940(2000), shield 0x7fba81c35bd0(2001)
Mar 20 18:29:27 --- last message repeated 1 time ---
Mar 20 18:29:27 {COMPUTER NAME} WindowServer[218]: device_generate_lock_screen_screenshot: authw 0x7fba81c2e940(2000)[0, 0, 1920, 1080] shield 0x7fba81c35bd0(2001), dev [1920,1080]
Mar 20 18:29:27 {COMPUTER NAME} com.apple.xpc.launchd[1] (com.apple.xpc.launchd.domain.user.502): Service "com.apple.xpc.launchd.unmanaged.loginwindow.72" tried to hijack endpoint "com.apple.tsm.uiserver" from owner: com.apple.SystemUIServer.agent
Mar 20 18:29:30 --- last message repeated 1 time ---
Mar 20 18:29:30 {COMPUTER NAME} kernel[0]: PM response took 4741 ms (30, powerd)
Mar 20 18:29:30 {COMPUTER NAME} kernel[0]: ARPT: 1632.007298: AirPort_Brcm43xx::powerChange: System Sleep
Mar 20 18:29:30 {COMPUTER NAME} kernel[0]: ARPT: 1632.007302: wl0: powerChange: *** BONJOUR/MDNS OFFLOADS ARE NOT RUNNING.
Mar 20 18:29:30 {COMPUTER NAME} kernel[0]: [0x1b014fb000, 0x19000000]
Mar 20 18:29:30 {COMPUTER NAME} kernel[0]: [0xd8ec7000, 0x19000000]
Mar 20 18:29:30 {COMPUTER NAME} kernel[0]: [0x1369ac0000, 0xe000000]
Mar 20 18:29:30 {COMPUTER NAME} kernel[0]: [0x0, 0x0]
Mar 20 18:29:31 {COMPUTER NAME} kernel[0]: hibernate image path: /var/vm/sleepimage
And when I wake it up by repeatedly pressing the power button:
Mar 20 18:30:09 {COMPUTER NAME} kernel[0]: hibernate_newruntime_map time: 0 ms, IOHibernatePollerOpen(), ml_get_interrupts_enabled 0
Mar 20 18:30:09 {COMPUTER NAME} kernel[0]: IOHibernatePollerOpen(0) 19 ms
Mar 20 18:30:09 {COMPUTER NAME} kernel[0]: hibernate_machine_init reading
Mar 20 18:30:09 {COMPUTER NAME} kernel[0]: PMStats: Hibernate read took 355 ms
Mar 20 18:30:09 {COMPUTER NAME} kernel[0]: hibernate_machine_init pagesDone 212628 sum2 2c66736a, time: 355 ms, disk(0x20000) 447 Mb/s, comp bytes: 57749504 time: 55 ms 985 Mb/s, crypt bytes: 157388800 time: 67 ms 2228 Mb/s
Mar 20 18:30:09 {COMPUTER NAME} kernel[0]: Wake reason: EC.PowerButton (User)
Mar 20 18:30:09 {COMPUTER NAME} kernel[0]: vm_compressor_fastwake_warmup (7450 - 12878) - starting
Mar 20 18:30:09 {COMPUTER NAME} kernel[0]: Previous sleep cause: -60
Mar 20 18:30:09 {COMPUTER NAME} kernel[0]: Previous shutdown cause: 5
Mar 20 18:30:09 {COMPUTER NAME} kernel[0]: AppleThunderboltNHIType2::prePCIWake - power up complete - took 0 us

Answer 1

This happened again at about 31% power, again unplugged.   Previously, I had plugged in the power before pressing the power button, but this time I pressed the power button before plugging in.  The display showed me the out of power icon.  Only on plugging it back in was I able to power up the laptop again.
Is it possible there's a bug either with the displayed power or how remaining power is detected?