That is very strange - I've not seen anything like that before. There doesn't appear to be anything strange about your system other than running under VMWare. I know there are 1000s of rclone users using 18.04 as it is the last LTS and I haven't had any similar bug reports.
Maybe some rclone -> kernel -> VMWare interaction. The kind of thing that is really hard to debug alas
I don't know whether you can attach a virtual serial console and make sure the kernel logs go there? You might get something out of the kernel as it dies. I've used that technique on physical machines with hard lockups.
I don't know whether your video was of the actual console of the machine - if not it might be worth looking at that.
You could also try Magic SysRq on the normal console. It is a little difficult to access so practice before the lockup!
It was an SSH console used for the video, but I've used the virtual console and it was the same results. The "actual" console on an ESXi server is something different, and can't be used to show the output from a VM as far as I know. I have not tried a serial console with an ESXi VM before, but I know I can share a serial port with the VM so It should be possible to hook up a serial console to it. I can do a SysRq at the virtual console. I'll try both of those and see if I get any results.
I have experienced this on MacOS, almost to a T--with the addition of not being able to re-launch the GUI after killing it. But that seems consistent with the behavior you are seeing.
I have trouble duplicating it, so can you give some more info on what you are doing besides simply running rclone sync? It looks like in the video there isn't anything else happening on the system, but in my case it seemed like it was happening when I had a file open on a mount, plus was copying to the same bucket, maybe other stuff, but just what I would consider "heavy load" and definitely maxing out my upload and download bandwidth.
I experienced this with rclone mount not rclone sync as I don't use that function very much. My thought had been that it was a FUSE issue, but now I actually think it's an issue with the GO runtime. At least for me, rclone logs no errors.
It, essentially, just acts as though time has stopped (e.g. no timeouts, no errors, just sits there). Sound about right? And, just to confirm, this is always reproducible for you, correct?