Hi there @amthomas,

I think that this could be caused by some really high workload on the Droplet so that the whole server gets unresponsive and the monitoring agent is unable to collect any data.

What I would usually do in this case is to put together a short script to note down the processes to a log file so that I could review them later on after the spike and try and figure out what exactly happened. Here is an example script that you could use:

https://www.digitalocean.com/community/questions/how-to-find-the-processes-that-are-consuming-the-most-server-resources

Another approach rather than using a custom script is to use SAR/systat instead. The sar command allows you to capture the utilization of your resources like RAM, CPU, Disk I/O and etc.

Here is how to install and configure it on Ubuntu:

https://www.digitalocean.com/community/questions/how-to-install-and-configure-sar-sysstat-on-ubuntu

Hope that this helps!
Regards,
Bobby