Sounds like the strings are getting hung up on something, most likely the string tree. Loosen the strings and rub a number 2 pencil on the underside of the tree and in nut slots. Tune the guitar back up and see if it still happens.

Check string on those saddles , there are maybe a chip on the saddles ? The saddle surface are not smooth ?

I had that ping noise from the string binding in the nut when I went up a gauge in string size. graphite fixed it but made the slot dirty looking. I started using watch movement oil Moebius Synt-A-Lube 9010 on all string contact points. it works better than anything else I have tried.

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as stated sounds like a string binding in the nut or the nut is worn and the string is moving in the nut slot , hth , cheers
Alan

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