You need to go back to "square 1".
My suggestion is that you call MTH and ask a tech to help you reset all 3 WIUs back to their true factory settings.
Then, set the WIUs up in a basic configuration without doing any fiddling with settings. That will establish a baseline before you modify anything that you shouldn't.
Further, unless you have a high confidence that you understand how things work, stay away from LuCI in the future, except for firmware updates. While adjusting settings may allow your WIUs to come online a bit faster, the down side is, as you
You've learned, the hard way, that by using LuCI to adjust WIU settings, you can cause serious self-inflicted problems.