Dmesg shows that Bluetooth fails to load its firmware after resume.
This happens 1726 times out of 2000 S3 cycles we tested.

[  384.026665] Bluetooth: hci0: Bootloader revision 0.0 build 26 week 38 2015
[  384.026666] acpi LNXPOWER:02: Turning OFF
[  384.028800] PM: Finishing wakeup.
[  384.029041] pcieport 0000:00:1d.0: PCI bridge to [bus 04]
[  384.029675] Bluetooth: hci0: Device revision is 16
[  384.029676] Bluetooth: hci0: Secure boot is enabled
[  384.029676] Bluetooth: hci0: OTP lock is enabled
[  384.029676] Bluetooth: hci0: API lock is enabled
[  384.029677] Bluetooth: hci0: Debug lock is disabled
[  384.029677] Bluetooth: hci0: Minimum firmware build 1 week 10 2014
[  384.029691] bluetooth hci0: Direct firmware load for intel/ibt-12-16.sfi failed with error -2
[  384.029692] bluetooth hci0: Falling back to syfs fallback for: intel/ibt-12-16.sfi
[  384.029702] WARNING: CPU: 0 PID: 76 at /kbuild/src/x86_64/drivers/base/firmware_loader/fallback.c:613 firmware_fallback_sysfs+0x37c/0x480
[  384.029702] Modules linked in: snd_hda_codec_hdmi snd_hda_codec_conexant snd_hda_codec_generic ledtrig_audio intel_rapl intel_pmc_core x86_pkg_temp_thermal sd_mod intel_powerclamp coretemp sg kvm irqbypass snd_soc_skl snd_soc_skl_ipc crct10dif_pclmul crc32_pclmul snd_soc_sst_ipc crc32c_intel i915 snd_soc_sst_dsp hid_multitouch ghash_clmulni_intel snd_hda_ext_core snd_soc_acpi_intel_match snd_soc_acpi hp_wmi snd_soc_core sparse_keymap wmi_bmof snd_compress snd_hda_intel btusb btrtl btbcm snd_hda_codec btintel iwlwifi uvcvideo snd_hda_core videobuf2_vmalloc aesni_intel snd_hwdep crypto_simd snd_pcm videobuf2_memops drm_kms_helper snd_timer bluetooth videobuf2_v4l2 cryptd syscopyarea mei_me sysfillrect cfg80211 ahci glue_helper snd pcspkr videobuf2_common sysimgblt fb_sys_fops libahci ecdh_generic i2c_i801 soundcore processor_thermal_device serio_raw int3400_thermal i2c_designware_platform libata i2c_designware_core drm videodev rfkill joydev mei hp_accel int3403_thermal intel_soc_dts_iosf
[  384.029728]  wmi i2c_hid lis3lv02d int340x_thermal_zone pinctrl_sunrisepoint video pinctrl_intel acpi_thermal_rel input_polldev acpi_pad hp_wireless pcc_cpufreq ip_tables
[  384.029732] CPU: 0 PID: 76 Comm: kworker/u17:0 Not tainted 5.1.0 #1
[  384.029733] Hardware name: HP HP ZHAN 66 Pro G1/83FD, BIOS Q93 Ver. 01.02.01 09/01/2017
[  384.029745] Workqueue: hci0 hci_power_on [bluetooth]
[  384.029748] RIP: 0010:firmware_fallback_sysfs+0x37c/0x480
[  384.029749] Code: e9 da fc ff ff 48 8b 8d 88 00 00 00 48 c7 c2 3a 9c f2 9f 4c 89 fe 48 c7 c7 78 02 41 a0 e8 0c 54 e9 ff e9 96 fe ff ff 89 04 24 <0f> 0b 48 c7 c6 40 9d f2 9f 48 89 ea 4c 89 ef e8 31 76 fe ff 8b 04
[  384.029750] RSP: 0018:fffface68114bc58 EFLAGS: 00010286
[  384.029750] RAX: 00000000fffffff5 RBX: 0000000000000001 RCX: 0000000000000000
[  384.029751] RDX: ffffffffa0261288 RSI: 0000000000000293 RDI: 0000000000000293
[  384.029751] RBP: fffface68114bd80 R08: ffffffffa0261288 R09: 0000000000022400
[  384.029751] R10: fffface68114bc38 R11: 0000000000000000 R12: 000000000000ea60
[  384.029752] R13: ffff93bd53bf4c28 R14: 0000000000000028 R15: 0000000000000000
[  384.029752] FS:  0000000000000000(0000) GS:ffff93bda8000000(0000) knlGS:0000000000000000
[  384.029753] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  384.029753] CR2: 00007f130037bf48 CR3: 000000014a60e002 CR4: 00000000003606f0
[  384.029754] Call Trace:
[  384.029757]  _request_firmware+0x4e9/0x660
[  384.029759]  request_firmware+0x32/0x50
[  384.029761]  btusb_setup_intel_new+0x130/0x510 [btusb]
[  384.029763]  ? _cond_resched+0x19/0x30
[  384.029763]  ? rpm_check_suspend_allowed+0x4c/0x90
[  384.029764]  ? __pm_runtime_idle+0x4e/0x90
[  384.029774]  hci_dev_do_open+0xd9/0x6d0 [bluetooth]
[  384.029775]  ? __switch_to_asm+0x34/0x70
[  384.029776]  ? __switch_to+0x8c/0x500
[  384.029777]  ? __switch_to_asm+0x34/0x70
[  384.029779] OOM killer enabled.
[  384.029779] Restarting tasks ... 
[  384.031411] pcieport 0000:00:1d.0:   bridge window [io  0x6000-0x6fff]
[  384.032383] done.
[  384.032878]  ? __switch_to_asm+0x40/0x70
[  384.032898]  hci_power_on+0x4e/0x240 [bluetooth]
[  384.032901]  ? __schedule+0x260/0x850
[  384.035061] pcieport 0000:00:1d.0:   bridge window [mem 0xb3000000-0xb30fffff]
[  384.036678]  process_one_work+0x19c/0x3c0
[  384.036681]  worker_thread+0x3c/0x3b0
[  384.038421] pcieport 0000:00:1d.0:   bridge window [mem 0x1c00000000-0x1c001fffff 64bit pref]
[  384.040206]  ? process_one_work+0x3c0/0x3c0
[  384.040207]  kthread+0x11e/0x140
[  384.040210]  ? kthread_park+0x90/0x90
[  384.105279]  ret_from_fork+0x35/0x40
[  384.105280] ---[ end trace cc0c4f62bacb67e7 ]---
[  384.105507] bluetooth hci0: firmware: intel/ibt-12-16.sfi will not be loaded