"425 Failed to establish connection" response from DS when using `rclone sync`

[JJGadgets]

Describe the bug
I am using rclone sync on a CronJob (in Kubernetes) to automate backing up my R4iLS flashcart's SD card.

I have successfully done the same for my N3DSXL's internal SD, but on my DS Lite with R4iLS, rclone gets a "425 Failed to establish connection" response from the DS after the rclone sync runs for a while.

To Reproduce
Steps to reproduce the behavior:

1. Run rclone sync ds: /data/ds
2. Let it run
3. After a few of its FTP operations, the 425 error starts to appear.

Expected behavior
No errors and successful transfers.

Screenshots
Sample rclone log

{"time":"2025-07-09T06:14:04.137278742+08:00","level":"error","msg":"Failed to copy: failed to open source object: open: 425 Failed to establish connection","object":"roms/nds/Need for Speed Carbon - Own the City (USA) (En,Fr,De,Es,It) old.sav","objectType":"*ftp.Object","source":"operations/copy.go:336"}

Platform (please complete the following information):

• System [e.g. 3DS]: DS Lite
• System version [e.g. 11.13.0-45]: Twilight Menu 27.15.0
• Launch method [e.g. rosalina 2.0.0]: Both R4iLS kernel and nds-bootstrap 2.6.0
• Type [e.g. 3dsx]: nds
• Classic? [Yes/No]: Yes

Additional context

Here's a link to my rclone Kubernetes deployment if you can understand it and it helps haha https://github.com/JJGadgets/Biohazard/blob/4272a100f68358a74a45c48c404ae8c6698b8849/kube/deploy/apps/rclone-retro/app/hr.yaml#L113-L129

[mtheall]

Try reducing rclone's number of concurrent connections. I would probably try --checkers 1 --transfers 1 --check-first to limit it to a single connection.

[JJGadgets]

@mtheall I do have concurrency 1 but not the others, I'll try it when I get back home in a week or so.

I also just found the tpslimit and bwlimit flags, if the flags you suggested don't work I'll try those too.

How would check-first help in this case?

[mtheall]

--check-first does the checks before any transfers
without it, it can check and transfer at the same time, using one checker connection and one transfer connection with the above options