Could indeed be that. I was able to sneak a refresh on another identical cluster (but which hadn't received it's full field list yet) with Safari (chrome wouldn't work). After that I dumped the .kibana from there, renamed one of the mappings to match what I actually needed to visualise and put it back to the production. Worked for now.
Looks like it's causing problems to other people too (according to the github issue), using browser memory to handle big mappings seems a bit weird 