This may have been by design by the author, but I wanted to mention this in case someone else stumbles into the issue I ran into.
I own a few LED strings of various lengths, so in an effort to speed up the creation of the presets in my WLED devices, I exported the preset JSON from one device, modify the lengths and import it back into another device. The initial JSON preset file is minified, so I formatted it to make it more human-readable and ease of editing. After I imported the formatted JSON file back into a WLED device, I noticed that it works just fine. However, if I make a modification to a preset that has a formatted JSON file, the WLED device would disconnect from Wi-Fi and would not return. Luckily, in my case, I have a button in my device, so was able to get the device into hotspot mode and reconnect. Upon examination of the resulting JSON file, I found that by modifying a preset, WLED had produced an ill-formed JSON file. I repeated the exercise with a minified JSON file, and everything worked just fine.
Lesson learned for me: Minified the JSON preset file before importing back into the WLED device.