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Thank you for posting your inquiry in this Community.
Intel ®Customer Service no longer responds to telephone, chat, or e-mail inquiries for the DN2800MT2 but you may want to try our Discontinued Products Community to get recommendations from fellow community members. You may also find the Discontinued Products Website helpful to address your request.
Regarding your Intel® Dual Band Wireless-AC 3160, based on the brief description, it might be defective, however as a last step troubleshooting step you can try to reinstall the OS with the previously used image(without the updates) to check if that makes any difference.
If that does not work , the best recommendation is to get in touch with your original place of purchase so you can get your Wireless card replaced.
I hope this helps.