Suspend with pm-suspend (or any other way) stops working after a few cycles

I had a fresh installation of Ubuntu-18.04. From the beginning suspend was failing spuriously. When I looked up in Google, I was suggested to upgrade my kernel as the provided kernel 4.15 was buggy. So I compiled the kernel from source and upgraded to 5.04. The problem still persisted. Having GRUB_CMDLINE_LINUX_DEFAULT="acpi_sleep=nonvs" in the file /etc/default/grub and running sudo update-grub does not change anything. Finally I have narrowed down the problem to calling sudo pm-suspend directly. The command works perfectly fine until a few suspend-wakeup cycles have passed. After a few cycle, the screen blanks out and the system does not go to sleep. Nothing responds and I have to do a hard reboot after which everything works the same.

Release: Description: Ubuntu 18.04.2 LTS
Release: 18.04

pm-utils:
  Installed: 1.4.1-17
  Candidate: 1.4.1-17
  Version table:
 *** 1.4.1-17 500
        500 http://in.archive.ubuntu.com/ubuntu bionic/universe amd64 Packages
        500 http://in.archive.ubuntu.com/ubuntu bionic/universe i386 Packages
        100 /var/lib/dpkg/status

Expected pm-suspend to work every time. Instead, pm-suspend fails to put the system to sleep after a few cycles.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: pm-utils 1.4.1-17
Uname: Linux 5.0.4 x86_64
ApportVersion: 2.20.9-0ubuntu7.5
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Mon Apr 1 21:20:39 2019
InstallationDate: Installed on 2019-02-13 (47 days ago)
InstallationMedia: Ubuntu 18.04 LTS "Bionic Beaver" - Release amd64 (20180426)
PackageArchitecture: all
ProcEnviron:
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_IN
 SHELL=/bin/bash
SourcePackage: pm-utils
UpgradeStatus: No upgrade log present (probably fresh install)