Sequoia Intermittent Engine Knocking

About a year ago my Sequoia started up with a knocking sound, but the knocking went away after a few minutes. I ignored it because I thought the knocking was due to the fact that I was parked on a hill overnight and the oil just needed some time to circulate.

However, just recently, my Sequoia started up with the same knocking sound as last year, but this time I was parked on level ground, and it was only parked for about an hour or so. - And just like the first time, the knocking went away after a few minutes.

Here's a video of the knocking sound that occurred recently and sounds the same as the knocking from a year ago - 2010 Toyota Sequoia Knocking at Idle

Questions

1. What is the reason(s) for the intermittent knocking?
2. If the knocking is caused by a mechanical failure, shouldn't the knocking occur more than what I've experienced (only twice over a year)?
3. Can you identify the cause of the knocking from the video?

2010 Sequoia - 5.7L - 173k miles

 

Timing chain tensioner? Spun bearing?

 

Could be. Thanks for the tip.

If it's the tensioner, maybe it's just gunk'd up and gets stuck once in a while. I'm going to try flushing the engine with BG EPR 109. Crossing fingers.