Do you have another pair of earphones you can connect and see if the issue still persists. Check the earphone connector for damage. As a field technician, listening to music with my phone in my pocket, I have bent many of them. Basically, if the peice is bent in any way, the metal contacts are not touching completely in the headphone jack on the phone.
When either issues happens, check to see if the phone is getting extremely hot. It could potentially be overheating. That being said see if the phones shape has changed, like screen separating from the phone base and/or possible bulging from the back or the screen. The battery might be going bad and/or broken open.
If the orginal screen was not damaged during removal, reinstall it and see if the iPhone boots correctly. If it does then it could be the replacement screen causing issues. While the replacement screen is installed connect it to the computer with iTunes installed and see it is recognized. I’ve installed repacement screens, worked first time through. Then other repairs had to do it 4-5 times because the small connectors are not seated all the way down. Another place to check is if the home button Touch ID flex cable is sitting all the way down in the screen. I’ve connected the flex cable, installed the small metal cover, reconnected the screen, turned on the phone, booted all the way up and yet the touch screen was lagging and not functioning correctly. Found that even though the screen appeared to be flush with the iPhone base, it was actually slightly crooked, which causes the screen to work inconsistently. Important thing is to make sure iTunes recognizes the iPhone and all the data is intact.
Hi, Had the same problem as well. Your battery may have to be reset. Unplug laptop from AC power, remove back cover and unplug the battery. Unplug the cmos battery and hold down the power button for 30secs to drain any residual power that could still be on the motherboard. Plug the two batteries back in, put the cover back on. Plug in AC power and let it charge for a bit. Hopefully after you turn the laptop back on it should show a charge, unplug or while and see what happens. Good luck