[mmichaels1970]

Does not look like the typical knee lock issue.

I was looking for the same. I've seen large assemblies, like boot camp graduation, where guys just drop like flies. You're basically instructed from day 1-1 to NOT lock your knees. I'd assume that if you're standing honor guard for a former SCOTUS justice, you're probably trained well beyond that.

That said, I've done probably over 50 funerals and I've seen it happen a few times due to heat. Shifting from a more relaxed working uniform to full-dress and doing a more elaborate funeral detail can be a bit of a pain.

Also not sure how many hours of prep you might have to do before such a high-level event. I wouldn't rule out exhaustion either. I remember pulling a 48 hour straight "clean up" before a triennial inspection. I stressed having everything so perfect and ended up falling asleep right in front of the inspector during the initial briefing....I think he passed us out of sympathy.

[Lazamataz]

You're basically instructed from day 1-1 to NOT lock your knees.

Correct. I was also advised that flexing your thigh muscles from time to time can help keep the blood moving.