warjort

Perhaps your xray mod? 🙂 The error is actually some problem trying to render a silverfish in a mob spawner. Probably one of your mods (could be a graphical mod) doesn't handle this properly - there is no information in the log to say which one.

You have flickerfix and apoli installed, they are both trying to do the same fix for night vision. You can remove flickerfix, see: https://github.com/jeremiahwinsley/flickerfix/issues/1

Looks similar to this? https://www.minecraftforum.net/forums/support/server-support-and/3133612-minecraft-server-1-16-5-crash 60 second server tick watchdog crash with performant installed.

The crash says you only have 157M free physical memory (of 8145M not 16G?) and 113M free swap memory (of 32721M). It currently has 2538M physical memory allocated but it wants to allocate approx 1.4G more memory which is not possible with only 157+113 = 270M available You probably need to close down other programs while running minecraft to free up memory. I would not recommend running java programs with large amounts of swap memory, it can cause lots of lag when memory needs to paged to and from disk. Your command line says you allocated 6G for java heap, but you obviously haven't used all that yet. You could also try reducing this value.