Downloading part of a file via /get_temporary_link with Range header returns incorrect content-type

I managed to reproduce this with a small file file.txt contents shello and using

rclone cat --offset 3 dropbox:file.txt -vv --dump bodies

This made this request

2023/04/25 11:20:46 DEBUG : HTTP REQUEST (req 0xc0009fec00)
2023/04/25 11:20:46 DEBUG : POST /2/files/download HTTP/1.1
Host: content.dropboxapi.com
User-Agent: rclone/v1.63.0-beta.6980.470db6bcd
Content-Length: 0
Authorization: XXXX
Content-Type: application/octet-stream
Dropbox-Api-Arg: {"path":"id:qqS0afUHwS0AAAAAAA6Nig"}
Range: bytes=3-6

And this response which appears to have muddled up the body with the header

2023/04/25 11:20:47 DEBUG : HTTP RESPONSE (req 0xc0009fec00)
2023/04/25 11:20:47 Unsolicited response received on idle HTTP channel starting with "\"\n \n\x18application/octet-stream\x12\x04llo\n"; err=<nil>
2023/04/25 11:20:47 DEBUG : HTTP/1.1 206 Partial Content
Content-Length: 4
Accept-Encoding: identity,gzip
Accept-Ranges: bytes
Content-Range: bytes 3-6/7
Content-Security-Policy: sandbox allow-forms allow-scripts
Content-Type: application/grpc
Date: Tue, 25 Apr 2023 10:20:46 GMT
Dropbox-Api-Result: {"name": "file.txt", "path_lower": "/file.txt", "path_display": "/file.txt", "id": "id:qqS0afUHwS0AAAAAAA6Nig", "client_modified": "2022-11-09T12:59:37Z", "server_modified": "2022-11-09T12:59:41Z", "rev": "5ed093ae1400f082af73a", "size": 7, "is_downloadable": true, "content_hash": "483068e5287bde73b67923dae8c200d461d80997108030841a082e628489993b"}
Etag: W/"5ed093ae1400f082af73a"
Original-Content-Length: 4
Server: envoy
Strict-Transport-Security: max-age=31536000; includeSubDomains; preload
X-Dropbox-Request-Id: e186d6db20684aee82e1123611632a3a
X-Dropbox-Response-Origin: far_remote
X-Robots-Tag: noindex, nofollow, noimageindex