We're seeing this error at toolkit.radicalroutes.org.uk, e.g. at
https://toolkit.radicalroutes.org.uk/index.php?title=Different_types_of_housing_co-ops&action=edit
I'm fairly new to this so hopefully it's something simple that we're missing or that I'm misunderstanding. Any help appreciated. Thanks!
Resolved before this post was approved! 
I needed to update JsonConfig - prev: 1.1.1 (01a703e), now: 1.2.0 (f3e7ec2)