Another update, I've been getting the error again, but only on the first time I load the page (every time i restart my browser) and only until I load a project, after which it works normally. It seems to be an issue with loading the default project? Not sure, just my best guess.
Okay, thanks; seems that I would have to add some error logging facility to the tool in order to make it easier to reproduce this kind of problem:
https://github.com/haroldo-ok/vcs-game-maker/issues/56