Invalid array length when dragging component onto canvas

Here's another clue... once the canvas "breaks" (which I can reliable make happen by refreshing the page and forcing a load... this behavior doesn't happen on new templates, only when the template is loaded from my custom storage, but I verified the JSON hasn't been corrupted), if I take a component and drag it over the canvas, it creates "ghost" copies of the component, even though I haven't dropped it. Every time I hover to the top of the canvas, a new ghost component is created - again, even though I haven't dropped. Image below:

Any thoughts welcome, thanks!

OK,

I managed to stick grapes.js into my Angular project and reference it instead of the minified version, so I could get more insight into what is going on. The problem seems to be in Sorter.js. The findPosition method is tasked with figuring out which element the cursor is hovering over. For some reason, this line of code:

result.indexEl = dim[6]; // If it's not in flow (like 'float' element)

Is coming back NaN. This is tricking all the way through the code and causing an invalid array length.

When I look at the dims, which is a two dimensional array with all of - I guess? - the dimensions of the components on the canvas, I see:

So... this is interesting. What I'm guessing is happening is that whatever's causing #2494, is creating a ghost component that has no location... and thus is causing THIS error.

I'll leave this ticket open but add my findings to #2494.