Inconsistency in APIv1 /polylines endpoint

[einrobin]

Describe the bug

There seems to be an inconsistency when retrieving more than 3 checkins in one request on the polyline endpoint:

In this case "features" is an array
traewelling.de/api/v1/polyline/2709772,2709943,2704568

In this case "features" is an object
traewelling.de/api/v1/polyline/2709772,2709943,2704568,2677553

From https://geojsonlint.com/

Steps to reproduce

Run two commands, notice the difference in the type of the features entry:

curl https://traewelling.de/api/v1/polyline/2709772,2709943,2704568
curl https://traewelling.de/api/v1/polyline/2709772,2709943,2704568,2677553

The issue doesn't appear to happen when requesting the endpoint while being logged in in the Browser. For this just try to open the following URL in your browser while logged in and while not logged in: https://traewelling.de/api/v1/polyline/2709772,2709943,2704568,2677553

Browser console logs

No response

Browser

Edge, Chrome, NodeJS, cURL

[einrobin]

Might also be related to #1907?