Sytem freezes at unexpected moments

My system will freeze periodically. When this happens there is no response from the machine (I cannot even switch to the F3-F7 terminals).

There doesn't seem to be an easily identifiable pattern:
- It happens when I'm using "Ubuntu Wayland" and the X version of gnome3 called "Ubuntu".
- At times this will happen while using a web browser, at other times while editing a file with vi in the terminal.
- Memtest86 does not show any memory errors.

This is happening roughly once every couple of days and is getting in the way of my work.
I was having problems booting the machine that have been solved: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1792100 .

Would anybody please have an idea of how I could debug this issue?

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After the last freeze there were not error message in /var/log/kern.log and in /var/log/syslog I found only these innocuous looking error messages before the freeze:

Jan 10 11:28:21 winters org.gnome.SettingsDaemon.MediaKeys.desktop[5959]: IPDL protocol error: Handler returned error code!
Jan 10 11:28:21 winters org.gnome.SettingsDaemon.MediaKeys.desktop[5959]: ###!!! [Parent][DispatchAsyncMessage] Error: PLayerTransaction::Msg_ReleaseLayer Processing error: message was deserialized, but the handler returned false (indicating failure)
Jan 10 11:28:26 winters systemd-resolved[1075]: Server returned error NXDOMAIN, mitigating potential DNS violation DVE-2018-0001, retrying transaction with reduced feature level UDP.

MY SETUP:

Ubuntu 18.10 with Gnome3 (both Wayland and X)
Linux 4.20.0-042000-generic #201812232030

Intel Xeon(R) CPU E5-2620 v4 @ 2.10GHz × 32
03:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Oland GL [FirePro W2100]