Lenovo X220T bluescreen with problems shutting down

We have several Lenovo X220T with Windows 8 x64 which are occasionally causing DRIVER_POWER_STATE_FAILURE (0x0000009f) bugcheck/bluescreens. The systems are using OEM drivers for most everything and the issue does not seem to be related to any one individual use case.

Upon shutdown, the system hangs at the "Shutting Down" spinner. Plugging in or removing any device does not cause an appropriate plug event to occur on the machine, and the device is not usable.

After examining the memory dump, it was determined that the Lenovo OEM Broadcom Bluetooth driver (btwampfl.sys) was taking the PnP lock and never releasing it. Updating the Bluetooth adapter to the latest Windows Update drivers resolved the issue. Full stack trace below:

Call Site
-----------------------------------
nt!KiSwapContext+0x76
nt!KiCommitThreadWait+0x23c
nt!KeDelayExecutionThread+0x1d3
btwampfl+0xa5c6
btwampfl+0xa1f7
bthport!BthHandleRemoveDevice+0xdf
bthport!BthHandlePnp+0xea
bthport!BthDispatchPnp+0x68
nt!IopSynchronousCall+0xc7
nt!IopRemoveDevice+0x100
nt!PnpRemoveLockedDeviceNode+0x22d
nt!PnpDeleteLockedDeviceNode+0x78
nt!PnpDeleteLockedDeviceNodes+0xa1
nt!PnpDelayedRemoveWorker+0x80
nt!ExpWorkerThread+0x142
nt!PspSystemThreadStartup+0x59
nt!KiStartSystemThread+0x16