Undefined next / Catch for all promise chains

[BartBucknill]

I'm seeing '(node:1504) UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 1): ReferenceError: next is not defined' in terminal from some routes.

Somewhere next() is called, but is not defined (presumably not in the parameters), and this error also indicates that a .catch is probably missing in this promise chain, although it may be possible to have this error even when it is handled (https://stackoverflow.com/questions/40500490/what-is-an-unhandled-promise-rejection).