Removed the layouts plugin and the location plugin and the problem resolved itself for now. Because its really late my time I haven’t had a chance to isolate whether one or both or none are causing the issue, but @angus@merefield giving you a heads up.
I didn’t have a chance to check the errors before I took down the plugins. And then today I rebuilt Discourse to 2.6.0.beta6 ( e7bad9f05d ). Problem went away.
A basic question, how does one know which plugin is taking how much CPU and memory? htop only shows the unicorn workers but not much resource each plugin is utilizing.