One of our Customer is getting TCP RST intermittently for specific API calls

Brief: The issue here is this connection reset does not happen every time, but some times like from 10 requests it is 3 times. The request flow is from Customer → CF WAF → API endpoint (internal api/service calls) → CF WAF → response back to Customer (Success/ Reset).
I have shared screenshot of RST from pcap file shared by our customer on our request. What could be the possible reason and how can it be resolved?
Please, suggest the possible solution and where exactly it can be fixed.

Anyone please look into this issue and guide here?

There are several reasons Cloudflare (or an intermediary firewall) might choose to reset the connection. Without more information it is impossible to tell what might be causing this. Are you able to reproduce the issue yourself? Do you see any events in your Cloudflare Firewall Logs associated with these requests?

Thank you for your response @albert .
The API and internal call at our end but it can only be checked from Client’s end. 2 times CF support was on call with them and we did live debug session. Still, they are not getting problem. Also, on CF there is no log captured when it is “Connection reset”, seems before it is passing through CF it says RST. Hope this helps.

On request of pcap file, we got this from client.
One more screenshot is here with more packets

With more information related on wireshark,

Could anyone please help with this?

Unfortunately, I don’t think anyone from the community will be able to help with this - especially since there’s no way for us to reproduce this issue. I would recommend opening a ticket with Cloudflare Support.

I created, thanks.

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