Ubuntu 20.04 cannot go to suspend. X applications are closed after try to suspend

Hello. I have a computer with Ubuntu 20.04. After installation of Ubuntu 20.04 suspend worked fine, but some time ago it stopped to work.

I press Suspend button in the menu, after that screen becomes black for a few seconds but fans continue rotation. After that screen turns on and I see a login screen. When I input the password, I see that all X applications were destroyed.

I tried different kernels, but result is the same.

cat /proc/acpi/wakeup command gives the next result:

Device S-state Status Sysfs node
PS2K S3 *enabled pnp:00:03
PS2M S3 *disabled pnp:00:04
IP2P S3 *disabled
XHCI S4 *enabled pci:0000:00:14.0
EHC1 S4 *enabled pci:0000:00:1d.0
EHC2 S4 *enabled pci:0000:00:1a.0
RP01 S4 *disabled pci:0000:00:1c.0
RP02 S4 *disabled
RP03 S4 *disabled
RP04 S4 *enabled pci:0000:00:1c.3
RTLG S4 *disabled pci:0000:06:00.0
RP05 S4 *disabled
RP06 S4 *disabled
RP07 S4 *disabled
RP08 S4 *disabled
RTLA S4 *disabled
BR1A S4 *enabled pci:0000:00:01.0
BR1B S4 *enabled pci:0000:00:01.1
BR2A S4 *enabled pci:0000:00:02.0
BR2B S4 *disabled
BR2C S4 *disabled
BR2D S4 *disabled
BR3A S4 *enabled pci:0000:00:03.0
BR3B S4 *disabled
BR3C S4 *disabled
BR3D S4 *disabled
QRP0 S4 *disabled
QR1A S4 *disabled
QR1B S4 *disabled
QR2A S4 *disabled
QR2B S4 *disabled
QR2C S4 *disabled
QR2D S4 *disabled
QR3A S4 *disabled
QR3B S4 *disabled
QR3C S4 *disabled
QR3D S4 *disabled
RRP0 S4 *disabled
RR1A S4 *disabled
RR1B S4 *disabled
RR2A S4 *disabled
RR2B S4 *disabled
RR2C S4 *disabled
RR2D S4 *disabled
RR3A S4 *disabled
RR3B S4 *disabled
RR3C S4 *disabled
RR3D S4 *disabled
SRP0 S4 *disabled
SR1A S4 *disabled
SR1B S4 *disabled
SR2A S4 *disabled
SR2B S4 *disabled
SR2C S4 *disabled
SR2D S4 *disabled
SR3A S4 *disabled
SR3B S4 *disabled
SR3C S4 *disabled
SR3D S4 *disabled

journalctl -b | grep suspend command shows next errors:

feb 05 21:00:17 user-pc gsd-power[1888]: Unable to inhibit suspend: GDBus.Error:org.freedesktop.DBus.Error.NoReply: Message recipient disconnected from message bus without replying
feb 05 21:00:17 user-pc gsd-power[2610]: Unable to inhibit suspend: GDBus.Error:org.freedesktop.DBus.Error.NoReply: Message recipient disconnected from message bus without replying
feb 05 21:00:17 user-pc gsd-media-keys[2607]: Unable to inhibit suspend: GDBus.Error:org.freedesktop.DBus.Error.NoReply: Message recipient disconnected from message bus without replying
feb 05 21:00:17 user-pc gsd-media-keys[1874]: Unable to inhibit suspend: GDBus.Error:org.freedesktop.DBus.Error.NoReply: Message recipient disconnected from message bus without replying

I tried to install Unity desktop instead of Gnome but result is the same except it doesn't kill X applications.

In my /var/log/syslog I see the next troubles connected with suspend:

Feb 8 21:39:04 user-pc ModemManager[1208]: <warn> [sleep-monitor] inhibit failed: GDBus.Error:org.freedesktop.DBus.Error.NoReply: Message recipient disconnected from message bus without replying
Feb 8 21:39:04 user-pc upowerd[1420]: Could not acquire inhibitor lock: GDBus.Error:org.freedesktop.DBus.Error.NoReply: Message recipient disconnected from message bus without replying
Feb 8 21:39:04 user-pc systemd[1]: systemd-logind.service: Main process exited, code=exited, status=1/FAILURE
Feb 8 21:39:04 user-pc systemd[1]: systemd-logind.service: Failed with result 'exit-code'.

pm-suspend suspends normally but sometimes fails to wake up.

Could you help me?