Failed uploading test results: an unexpected storage error occurred

I have been trying to upload test results from an xml file generated by pytest to circleci but it always fails to do so with the error:

failed uploading test results: an unexpected storage error occurred

the available explanations suggest that either my xml file does not exist or circleci does not have the right permissions to access that file. I checked both and it seems to be fine. Running the command

ls -l path/to/test-results

returns

-rwxrwxrwx 1 circleci circleci 312 Sep 14 20:38 junit.xml

which means my xml file exists and all users have the access to read, write and execute it… Would appreciate your insight into this matter. thanks.