Gnome is hanging randomly for 1 minute or so. The mouse cursor still moves, but all windows and content freezes. The seconds display on the clock stops moving.
One weird thing (may be coincidence) that I just noticed while doing this bug is the hang always stops when the clock reads xx:xx:07 (ie, the seconds is always 07)
The following are two instances from /var/log/syslog (I report them both as the same bug because the symptoms are the same and the last two lines in the log are the same);
INSTANCE 1:
Mar 27 18:53:09 dragonfly gnome-session[1605]: ** (soffice:17185): WARNING **: Unknown event notification 34
Mar 27 18:53:13 dragonfly gnome-session[1605]: ** (soffice:17185): WARNING **: Unknown event notification 36
Mar 27 18:53:13 dragonfly gnome-session[1605]: ** (soffice:17185): WARNING **: Unknown event notification 36
Mar 27 18:53:13 dragonfly gnome-session[1605]: ** (soffice:17185): WARNING **: Unknown event notification 34
Mar 27 18:53:32 dragonfly gnome-session[1605]: Gjs-Message: JS LOG: Feed scaninbox Error:oAuth.acc_token is undefined
Mar 27 18:53:32 dragonfly gnome-session[1605]: Gjs-Message: JS LOG: onTimer :folder is not defined
INSTANCE 2:
Mar 27 19:01:06 dragonfly gnome-session[1605]: [1:1:0327/190106.317420:ERROR:KeyboardEventManager.cpp(427)] Not implemented reached in static bool blink::KeyboardEventManager::currentCapsLockState()
Mar 27 19:01:06 dragonfly gnome-session[1605]: [1:1:0327/190106.318769:ERROR:KeyboardEventManager.cpp(427)] Not implemented reached in static bool blink::KeyboardEventManager::currentCapsLockState()
Mar 27 19:01:07 dragonfly gnome-session[1605]: [1:1:0327/190107.192199:ERROR:KeyboardEventManager.cpp(427)] Not implemented reached in static bool blink::KeyboardEventManager::currentCapsLockState()
Mar 27 19:02:55 dragonfly dbus[994]: [system] Activating via systemd: service name='org.bluez' unit='dbus-org.bluez.service'
Mar 27 19:03:32 dragonfly gnome-session[1605]: Gjs-Message: JS LOG: Feed scaninbox Error:oAuth.acc_token is undefined
Mar 27 19:03:32 dragonfly gnome-session[1605]: Gjs-Message: JS LOG: onTimer :folder is not defined
ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: gnome-session 3.18.1.2-1ubuntu1.16.04.2
ProcVersionSignature: Ubuntu 4.4.0-66.87-generic 4.4.44
Uname: Linux 4.4.0-66-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.5
Architecture: amd64
CurrentDesktop: GNOME
Date: Mon Mar 27 19:07:56 2017
InstallationDate: Installed on 2016-12-27 (90 days ago)
InstallationMedia: Ubuntu-GNOME 16.04 LTS "Xenial Xerus" - Release amd64 (20160421)
PackageArchitecture: all
SourcePackage: gnome-session
UpgradeStatus: No upgrade log present (probably fresh install)
Post too my experience which seems similar to yours. I only see such 'minute' freeze when i'm working with libreoffice-calc (5.3.1 actually); here it is with a more recent version on Zesty 64 bits. (gnome-session 3.24.0-0ubuntu1)
You report against gnome-session, and myself can't decide if gnome-session has to be blamed or if soffice is faulty instead. What is sure is that bottleneck somewhere. This is irritating, for example, when you enter many data, and then find that some was written wrongly because the 'buffer' was not able to continue writting the exact order you typed the data.