Sending an 2xx 'early' response before end of request for non-POST endpoint

I have resources served by the assets controller, printing warning message like the one below. Every web search tells it is related to uploading files, which we are not doing in this project. What might produce this behavior?

Sending an 2xx 'early' response before end of request for http://HOST_REMOVED/assets/PATH_REMOVED/FILENAME_REMOVED.js received... Note that the connection will be closed after this response. Also, many clients will not read early responses! Consider only issuing this response after the request data has been completely read!

Asset configuration in routes file:
GET /assets/*file controllers.Assets.versioned(path="/public", file: Asset)