Scenario 1: 

•  Computer: Ubuntu Linux (latest). 4th Gen AMD Ryzen 9. Nvidia 1660 Video card. 
• Gamemode: Single Player - Hardcore - New world
• Error: Game crashes randomly but frequently while playing. Animals will stop moving, chests cannot be opened, blocks cannot be mined. It looks like a severe lag issue but its on a single player session. Exiting to save will never complete

Update: I tried removing my .minecraft directory and standing up a new world. It worked for 20 minutes or so and then every mob froze and I couldnt use anything. I also couldnt quit and the save reverted back. I'm thinking it might be something in the save routine. 

Scenario 2:

• Server: Centos 8. 8 core 16GB ram VM on a vmware hypervisor (running on a dell 710)
• Clients: 2 Ubuntu linux (latest) systems. 
• Gamemode: Multi-player Survival - New World
• Error: Frequent long stutters and crashes occur but actually not as frequent as with single player. System fails to save and does not notice if users disconnect. It will eventually seg fault the process if a user tries to disconnect and rejoin. 

Scenario 3: 

• Server: Centos 8. 8 core 16GB ram VM on a vmware hypervisor (running on a dell 710)
• Clients: 2 Ubuntu linux (latest) systems. 
• Gamemode: Multi-player Survival - Upgraded world from previous snapshot. Also occurs on hardcore single-player games from previous snapshot.
• Error: Any commands seem to instantly freeze the game. Animals stop moving, time stops progressing, etc. I've also seen this happen when trying to sleep. I cleared errors with old copper assets by removing the player and stats from the world, however this freezing persists.