Update rclone to the latest version
Do not use random stuff from random sources - better to use defaults in most cases.
e.g. --dropbox-batch-mode async does not guarantee successful writes. Do you have any special reason to use it?
What you need is to decide about cache mode and try to limit number of transactions (as Dropbox has heavily limited API)
by setting --tpslimit 12 --tpslimit-burst 0 otherwise you see what you see:
2023/06/06 18:51:19 ERROR : IO error: upload failed: too_many_requests/..
--transfers 32 is way too high for Dropbox - I would use default 4
Almost reference mount options for dropbox can be found in the link below.