You need to send your gun to someone who builds and/or knows Mp5s. Everyone you brought it to knows nothing about your gun. I would recommend Ralph at RDTS, he has been specializing in MP5s and other HKs for around 30 years. He has a detailed Instagram page under RDTS. Don't go to his website if you come across it as it is very outdated. I have two of his guns and he is a great guy to talk to.
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