Cool that you found the issue! 
My gut feeling is that you can’t disable the cache unfortunately… since anki was never really built for this kind of thing (as I understand it, the ability to use javascript at all is mostly just a byproduct of anki using html for the cards). So I don’t think there’s really any effort made to make it developer friendly.
I know too little (close to nothing actually) about plugins, så maybe it’d be possible via those, but if there was a cache-disabling plugin one would expect it to turn up in a google search…