Ford Explorer 4.0 What is that BAD NOISE? Timing chain?

My 2004 Ford Explorer 4.0 SOHC started making the noise in the video and I had no idea what it was. No video had exactly the right sound. Closest I could find was videos showing timing chain cassette or tensioner noises. But nothing quite fit perfectly. So I did a full rebuild, that solved the problem. But only for 3000 miles. Then the horrible noise again. Pulled the passenger side valve cover and could see the rear timing cassette was again toast. So I pulled the motor - again. Turned the engine over manually and still heard a noise from the front. So I took off the front cover and thats when I saw the jackshaft chain situation. So, I ordered up a new jackshaft tensioner (and rear cassette), put it back together and fired it up. Runs smooth again. I'm hoping I just had bad part and that this lasts way longer that 3000 miles this time. Happy to try to answer questions, but keep in mind I'm a DIY'er... Thank you for watching! I sincerely hope this helps you out.