Ubuntu 18.04.1 LTS get crashed

Dear supporter

We got a issue that the Ubuntu 18.04.1 LTS can’t reboot after some heavy CPU+MEMORY calc, it repro as " error: file ‘boot/grub/i6-pc/normal.mod’ not found".

And we found most of the files include system files are gong also.

It happened 4-6 times for the past month, we believe the hardware is ok, everytime it repro, we found CPU+MEMORY is very high for a long time, like 20 minutes even more.

so any issues related with it, anything we can do to avoid it?

Thanks
Louis.

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