Random POST request failures after upgrade from 9.2.4 to 10.0.4 or 10.2.0

## Description

After upgrading Apache Traffic Server from 9.2.4 to 10.0.4 or even 10.2.0 we are experiencing random issues handling POST requests.

The problem appears intermittently: some POST requests do not receive any response from ATS.
The client connection remains open until timeout.

This issue did not occur on version 9.2.4.

## Environment

- ATS Version: 10.0.4/10.2.0
- Previous Version: 9.2.4
- OS: Rocky 8
- Plugins enabled: @plugin=header_rewrite.so, regex_remap.so, cachekey.so, compress.so

## Expected Behavior

POST requests should be forwarded upstream and a valid response should be returned to the client.

## Actual Behavior

Some POST requests randomly hang.
No response is returned to the client.
The client eventually times out and fallback.
Read_timeout 30s --> this is reached for the fact that I don't get response

## Frequency

Approximately 15% of POST requests (random pattern).

## Steps to Reproduce

Unfortunately not deterministic, but with my config I'm able to reprodiuce it.

## Debug Logs

Below is a relevant excerpt from debug logs (http|cache.*|regex.*):

## Possible solution

Enable http2, the error rate drops close to 0. But why on ATS 9 I din't have this issue with http1.

[post_issue_ats10.txt](https://github.com/user-attachments/files/25581584/post_issue_ats10.txt)