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Hi l_b_w_l_b_w,

Welcome to the Apple Support Community. I do apologize for the quality issue you are having with your iPhone X. After looking at your post, it might seem that this issue is related to Hardware and not Software. Your iPhone might have to be viewed by your local Apple Store or your local Apple Authorized Service Provider (AASP). I would go through Apple Support and explain that you have done all the recommended troubleshooting steps.

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Best of Luck

-Apple_Tekh

Hi l_b_w_l_b_w,

Since the device is Out of Warranty (OFW) you might need to pay out of pocket for any repairs on the device. You can still make an appoiment with your local Apple Store or Apple Authorized Service Provider by just going to the physical store. You can also make an appoiment by speaking with an Apple Support Agent. If you want an even easier way of repairing your device, just use the send by mail. There your device will be sent to an Apple Authorized Repair Center where they can do the repair.

Apple Pricing Guide for Repairs

iPhone Repair - Official Apple Support

Best of Luck

-Apple_Tekh

Whereas you may have a hardware problem that needs attention it is just as likely to be software

The next step would be to restore your device, and setup the device without restoring a backup, to see if the issue is replicated. I would first make sure you have a backup so your data is saved.

Here is a guide for those steps:

How to back up your iPhone, iPad, and iPod touch

Restore your iPhone, iPad, or iPod to factory settings

and see how it goes

If no improvement send it for repair or replace

If it works well restore from backup but be prepared to wipe again without restore from backup. 

https://support.apple.com/en-us/HT204184