It's happened to me for as long as I can remember, across years of using it (so obviously multiple versions) and with or without other addons.
There are multiple things that happen, never really the same thing twice, so "bugged out" is the best i can come up with. An example is on the load conditions tab and I select a talent spec after checking the respective box to enable that option. The page (the content loaded by that tab, not the left-hand list of auras, just that area) becomes distorted, the form elements duplicate beneath, think of it as a segment of the page looping over and over downwards; it's almost like a screen error on a phone, it genuinely looks that distorted.
It's always some form of distortion like that or just nothing; the area is blank. I can close and re-open the GUI and it does nothing. Sometimes I'll get an LUA error message box with it (I run Swatter, I don't know if that box is default UI or not) but I usually won't. This will persist until I reload UI.
I can continue using WeakAuras without reloading UI, just not that one aura. If I'm modifying "Aura A" and this happens on the Trigger tab, I can continue working on other auras; I'll just need to reload to be able to continue on "Aura A".
I assumed this happened to other people just because there is no specific condition on my end. I have been through multiple versions of WA, on multiple computers, playing multiple toons, on multiple WoW accounts on multiple WoW builds through multiple EXPANSIONS, I've had multiple sets of addons running alongside it and even no addons, I've even had it happen on multiple operating systems (Windows 7, Windows 10, multiple versions of OSX).
If it's genuinely not happening to *anybody* else then I'm completely stumped as the only constant here is that it's my account and I'm the person physically using the machine; that's it. Honestly, I've got to assume it happens more frequently than realized but most people just don't take the time to report it, especially considering it's fixed by a reload. I think most people that have an addon bug out turn to "reload my UI" as the first possible solution, and when it works they just shrug it off; the percentage of people willing to leave a comment, let alone go to another site and submit an official but report, has got to be incredibly low. Add to that the fact that people are even less likely to report an issue that they can fix (albeit temporarily) via a reload UI, and it's gotta be even less. I mean, we all know that people are tremendously more likely to leave a comment or post a bug report if an issue genuinely prevents them from using the addon or playing the game, but otherwise I can't imagine there being a 1 to 1 ratio of reports to actual occurences.
if you can help me figure out how this would happen for so long across so many different variables I'd be happy to listen, but otherwise logic kinda dictates that it can't be isolated to me unless there's some other contributing factor I flat-out have not considered.
Edit: I can take a screenshot the next time it happens, if you'd like. I didn't plan on any extensive WA work in the next few days and it only happens once I've been playing around with things in there for a decent amount of time, but I can re-make the aura that bugged out my install (the issue in my original comment) to occupy some time and snap a screenshot when it inevitably bugs out again, requiring a reload. Would that help at all?