These types of errors seem to be normal (I see them all the time, even when things are working swimmingly).
But my API lists 3% error in 605,284 requests, and traffic is almost always below 1/s.
That is on an rclone crypt backed by gdrive that I constantly upload to and stream from.
For what it's worth: I had a similar problem --- API rate limit errors, etc. --- before. In my cause it was caused by a very specific bug relating to the way that I upload files:
$RCLONE copy --rc --rc-addr=${RCADDR} --rc-no-auth --stats=5m --stats-one-line \
--tpslimit=5 --transfers=10 --files-from-traverse --files-from=${CLOUDLIST} \
--fast-list --log-file=${LOGFILE} ${VERBOSE} ${TEST} "${SRC}" "${DST}"
Where $CLOUDLIST is a list of files ranging from a handful of large mkvs to hundreds of tiny nfo files. The --files-from-traverse flag is from a special build (v1.46.0-019-gf97cbd3b-fix-files-from-traverse-beta) that forces rclone to use the old method of listing files from the remote before starting an upload.
I have no idea if you are experiencing something similar (probably not, since you don't use --files-from) but you can read about my issues in this thread.