I upgraded my Ubuntu server from 16.04 to 18.04 a few days ago, and ever since, I've had issues with the Instance Manager. It started with my Minecraft (Sky Factory 3/FTB) server locking up* about five minutes or less into my starting the server from within the web interface. I have since wiped the entirety of the AMP Instance Manager, redownloaded it, and remade my Minecraft instance, and upon attempting to have the manager download the SF3 files, it locks up* upon "extracting archive".
*But when I say locks up... I mean, the entirety of my Ubuntu VM is dead. Hard lock. SSH, Plex, Samba file server, even the server console with ESXI is dead. I have to hard reset the entire VM (one VM serves all of these duties, given my hardware limitations currently).
I thought it was a Minecraft issue at first, but now that I can't even reinstall my Minecraft server through AMP, leads me to believe it's a problem with AMP and 18.04 somehow. After the issue started happening shortly after the 18.04 upgrade, I left the AMP manager offline and the server did its other jobs just fine, all day and night.
I apt-get update/upgrade frequently, and made sure that the required files in the AMP install process were there/updated before I did this.