I appreciate that, thank you. Based on the other thread that I linked where someone else had the exact same error that I did, I was concerned that my router was defective and needed to be sent back under warranty. I just wanted to diagnose my router to see if it also had "bad blocks on the NAND chip." Just because someone isn't as advanced as you, doesn't mean they are incapable of following instructions and being cautious. Plenty of people use Merlin firmware who aren't Mensa members.
Anyway, I did a hard reset of my router today using the WPS method. This time I disconnected my security system and a second Ethernet cable, so that the only Ethernet connected was going to my desktop. After I went through the initial process again, I was told that new firmware was available and chose to upgrade. The upgrade process was stuck and no further updates were given, even though it said it should take under 3 minutes. I opened another tab and logged into the router and was surprised to see that Merlin was still installed. I was under the impression that a hard reset would be a factory reset, so I'm a bit confused.
After doing another hard reset, I chose not to upgrade the firmware. Merlin was still installed. Before I went through the hassle of using the firmware restoration tool, I decided to try the manual update of the latest Merlin firmware again. It worked perfectly! I don't know what the problem was before. Maybe it was my security system or the fact that I was using a laptop?