I have upgraded my elastic / kibana stack from 7.12.1 to 7.16.2

Unfortunately and despite the fact that elasticsearch is now healthy, kibana is not loading due to a js error:

login:1 Refused to execute script from 'https://my-kibana.com/login?next=%2F39457%2Fbundles%2Fplugin%2Fdata%2Fdata.plugin.js' because its MIME type ('text/html') is not executable, and strict MIME type checking is enabled.

(there are other errors like this as well)

Any suggestions?