Why is my iPhone 7 in reboot/recovery mode loop?

5 weeks ago, I dropped my iPhone maybe 2 feet onto the ground. After rebooting twice, it worked just fine. About 3 weeks later, it began rebooting again and has not stopped since.

I know the problem isn't the battery because I'm about to get the phone into Recovery Mode (where the "Connect to iTunes" prompt appears) and have it stay there for extended periods of time. I'm also able to get the phone into DFU mode and had it stay in that mode for over an hour before I forced started it, so the battery shouldn't be an issue.

Currently, it is in Recovery Mode loop, where every time it turns on, it asks to be connected to iTunes. However, using ReiBoot, I can get it out of Recovery and back into the reboot loop, which isn't much better. I've tried both updating and restoring in both Recovery mode and DFU on both PC and Mac using a genuine Apple lightning cable, but every time, the iPhone reboots when iTunes gets to the "Preparing iPhone..." portion, looping back to Recovery Mode, and in the process giving me the 4013 error on iTunes.

Any help would be greatly appreciated.