Unexpected 301 status code in next.js document request

Sometimes when I tried to access the serverside rendered next.js route first I get a 301 status code with around a 1-second delay then it again fetches the same route which sends a 200 status code.

NOTE: we are not doing any manual redirects in our route.

I am not able to reproduce this. Do you mind sharing a HAR file (with preserve log option checked)? The only one I was able to see is:

Which is a 308 from trailing slash to non-trailing slash version.