Speedmaster "ping" every other beat

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I apologize if this is an obvious question; have searched around and only found 1 related thread on watchuseek.
My TinTin (145.0051) makes a metallic 'ping' every other beat when the watch is flat/parallel to the ground. Upon rotating if 90 degrees / perpendicular with the ground, it disappears. I removed the caseback and dust cover and the sound was gone, so am assuming something is bumping against the dust cover, not sure if it's an easy fix or requires formal service. No issues with the time/accuracy, not a serious issue unless there's potential for something to be wearing down over time.
Att'd movement pic and a brief audio link...the first few seconds one can hear the ping, which then disappears when I rotate vertically.
https://youtube.com/shorts/fVbK0L0RBAU (audio)

Thoughts?
 
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Could try a display caseback (such as spiralwinder). Wondering if that’ll fix the noise, and (as a bonus feature), look pretty cool

Other than that, if it isn’t messing up the timekeeping or causing damage, I would be inclined to leave it as is.
 
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It’s likely just some sort of resonance. Nothing to worry about.
 
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Take caseback and inner cover off and screw only the back in. No inner cover. Of noise is gone, might be something like an Echo Chamber effect. Does the inner cover sits tight and you have to pry it off ?
 
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Take caseback and inner cover off and screw only the back in. No inner cover. Of noise is gone, might be something like an Echo Chamber effect. Does the inner cover sits tight and you have to pry it off ?
It’s actually loose
 
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There is your problem. Bend a little dent into the area, where it fits the movement ring. Fit it again and, Voila ' . Ping gone. I hope....
 
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Your fine unless it pongs.