Compiz remarkably slows down after switching user Ubuntu 16.04

Hello,

Unity stops working on my Lenovo T420 laptop after I switch user during my X Window session and then come back to the original user session (for example, when I log out from the second user's session). It is possible to switch to the text console, but the system reacts after about 1 minute after pressing Ctrl-Alt-F1. It is normally responsive in the text mode and in the graphic mode, after I kill compiz (kill -9 pidoffcompiz) before, but after restarting compiz (or whole X Window system with system lightwm restart), again no response. I discovered an interesting work-around. When I close the lid of my laptop, it gets into doze mode after some 1 minute or so and the responsiveness returns back. This behavior doesn't occur every time.
Feb 17 20:12:03 hevelius kernel: [ 7509.316624] WARNING: CPU: 3 PID: 18889 at /build/linux-W6HB68/linux-4.4.0/drivers/gpu/drm/i915/intel_display.c:3965 intel_crtc_wait_for_pending_flips+0x1e2/0x240 [i915]()
Feb 17 20:12:03 hevelius kernel: [ 7509.316629] WARN_ON(wait_event_timeout(dev_priv->pending_flip_queue, !intel_crtc_has_pending_flip(crtc), 60*HZ) == 0)
Feb 17 20:12:03 hevelius kernel: [ 7509.316633] Modules linked in: nls_utf8 isofs nls_iso8859_1 xt_CHECKSUM iptable_mangle ipt_MASQUERADE nf_nat_masquerade_ipv4 iptable_nat nf_nat_ipv4 nf_nat nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack nf_conntrack ipt_REJECT nf_reject_ipv4 xt_tcpudp bridge stp llc ebtable_filter ebtables ip6table_filter ip6_tables iptable_filter ip_tables x_tables ctr ccm snd_hrtimer rfcomm bnep binfmt_misc arc4 iwldvm intel_rapl mac80211 x86_pkg_temp_thermal intel_powerclamp snd_hda_codec_hdmi thinkpad_acpi uvcvideo coretemp videobuf2_vmalloc videobuf2_memops videobuf2_v4l2 kvm_intel iwlwifi kvm videobuf2_core btusb irqbypass btrtl btbcm snd_hda_codec_conexant nvram v4l2_common btintel snd_hda_codec_generic snd_hda_intel snd_hda_codec snd_hda_core snd_seq_midi snd_seq_midi_event snd_rawmidi snd_seq snd_seq_device snd_hwdep bluetooth snd_pcm videodev cfg80211 snd_timer input_leds media joydev serio_raw snd soundcore mei_me mei shpchp lpc_ich mac_hid parport_pc ppdev lp parport autofs4 drbg ansi_cprng algif_skcipher af_alg dm_crypt uas usb_storage mmc_block i915 crct10dif_pclmul crc32_pclmul ghash_clmulni_intel aesni_intel aes_x86_64 i2c_algo_bit lrw gf128mul glue_helper ablk_helper cryptd drm_kms_helper psmouse syscopyarea sysfillrect sysimgblt fb_sys_fops e1000e ahci drm libahci sdhci_pci sdhci ptp pps_core wmi fjes video
The following is an excerpt of my syslog, probably relative to the issue.

Best Regards,
Adam Łacny

Feb 17 20:12:03 hevelius kernel: [ 7509.316791] CPU: 3 PID: 18889 Comm: Xorg Tainted: G W 4.4.0-62-generic #83-Ubuntu
Feb 17 20:12:03 hevelius kernel: [ 7509.316795] Hardware name: LENOVO 4180AG8/4180AG8, BIOS 83ET67WW (1.37 ) 11/28/2011
Feb 17 20:12:03 hevelius kernel: [ 7509.316799] 0000000000000286 000000007e065147 ffff8801ff763af8 ffffffff813f7c63
Feb 17 20:12:03 hevelius kernel: [ 7509.316806] ffff8801ff763b40 ffffffffc02f0ab8 ffff8801ff763b30 ffffffff810812d2
Feb 17 20:12:03 hevelius kernel: [ 7509.316811] ffff8800359c11a8 ffff88020f0f9030 ffff8802102b7000 ffff8800359c1000
Feb 17 20:12:03 hevelius kernel: [ 7509.316817] Call Trace:
Feb 17 20:12:03 hevelius kernel: [ 7509.316828] [<ffffffff813f7c63>] dump_stack+0x63/0x90
Feb 17 20:12:03 hevelius kernel: [ 7509.316838] [<ffffffff810812d2>] warn_slowpath_common+0x82/0xc0
Feb 17 20:12:03 hevelius kernel: [ 7509.316845] [<ffffffff8108136c>] warn_slowpath_fmt+0x5c/0x80
Feb 17 20:12:03 hevelius kernel: [ 7509.316854] [<ffffffff810c3d45>] ? finish_wait+0x55/0x70
Feb 17 20:12:03 hevelius kernel: [ 7509.316915] [<ffffffffc028b2e2>] intel_crtc_wait_for_pending_flips+0x1e2/0x240 [i915]
Feb 17 20:12:03 hevelius kernel: [ 7509.316923] [<ffffffff810c41e0>] ? wake_atomic_t_function+0x60/0x60
Feb 17 20:12:03 hevelius kernel: [ 7509.316978] [<ffffffffc028c561>] intel_pre_plane_update+0x111/0x140 [i915]
Feb 17 20:12:03 hevelius kernel: [ 7509.317029] [<ffffffffc028cad0>] intel_atomic_commit+0xf0/0x6f0 [i915]
Feb 17 20:12:03 hevelius kernel: [ 7509.317075] [<ffffffffc0086bde>] ? drm_atomic_check_only+0x18e/0x590 [drm]
Feb 17 20:12:03 hevelius kernel: [ 7509.317097] [<ffffffffc018e8c6>] ? __drm_atomic_helper_crtc_duplicate_state+0x56/0xa0 [drm_kms_helper]
Feb 17 20:12:03 hevelius kernel: [ 7509.317136] [<ffffffffc0087017>] drm_atomic_commit+0x37/0x60 [drm]
Feb 17 20:12:03 hevelius kernel: [ 7509.317156] [<ffffffffc018f51d>] drm_atomic_helper_connector_dpms+0xed/0x1a0 [drm_kms_helper]
Feb 17 20:12:03 hevelius kernel: [ 7509.317193] [<ffffffffc007b55c>] drm_mode_obj_set_property_ioctl+0x25c/0x270 [drm]
Feb 17 20:12:03 hevelius kernel: [ 7509.317227] [<ffffffffc007b5af>] drm_mode_connector_property_set_ioctl+0x3f/0x60 [drm]
Feb 17 20:12:03 hevelius kernel: [ 7509.317256] [<ffffffffc006b752>] drm_ioctl+0x152/0x540 [drm]
Feb 17 20:12:03 hevelius kernel: [ 7509.317288] [<ffffffffc007b570>] ? drm_mode_obj_set_property_ioctl+0x270/0x270 [drm]
Feb 17 20:12:03 hevelius kernel: [ 7509.317296] [<ffffffff8102d8c7>] ? __switch_to+0x437/0x5c0
Feb 17 20:12:03 hevelius kernel: [ 7509.317304] [<ffffffff812227af>] do_vfs_ioctl+0x29f/0x490
Feb 17 20:12:03 hevelius kernel: [ 7509.317311] [<ffffffff818344c5>] ? schedule+0x35/0x80
Feb 17 20:12:03 hevelius kernel: [ 7509.317316] [<ffffffff81222a19>] SyS_ioctl+0x79/0x90
Feb 17 20:12:03 hevelius kernel: [ 7509.317322] [<ffffffff81224b61>] ? SyS_poll+0x71/0x130
Feb 17 20:12:03 hevelius kernel: [ 7509.317329] [<ffffffff818385f2>] entry_SYSCALL_64_fastpath+0x16/0x71
Feb 17 20:12:03 hevelius kernel: [ 7509.317334] ---[ end trace a6fb9588037f962e ]---