Http Status 400 Error only while using ESP_SSLClient

[JoergTiedemann]

Hi
a few month ago we´ve had a discussion about a HTTP status 400 error while writing to realtime database (see discussion #330)
You help me a lot and we came to the conclusion that the reason for the error must be a hardware issue
Now I've tested with new hardware with more ram (ESP32-S3 devkit C-1 N16R8) and I´ve exactly the same http error status 400.
I've made a little research to find the reason and I've some questions I didn't understand and probably you can help me

I use ESP SSLClient as the network client:

In the definition:

WiFiClient basic_client;
ESP_SSLClient ssl_client;
using AsyncClientFB = AsyncClientClass;
AsyncClientFB aClient(ssl_client);

and in the code

    ssl_client.setClient(&basic_client);
    ssl_client.setInsecure();
    ssl_client.setBufferSizes(16384, 16384);

I write every 30 seconds to 3 realtimedatabase nodes asynchronous directly behind each other:

Database.set<object_t>(aClient, StatusPath.c_str(), object_t(jsonStatuspaylod.raw()),processDataStatus,"WriteFirebaseStatus");
Database.set<object_t>(aClient, DayPath.c_str(), object_t(jsonDaypayload.raw()),processDataDay,"WriteFirebaseDay);
Database.set<object_t>(aClient, LoggingPath.c_str(), object_t(jsonLoggingpayload.raw()),processDataLogging,"WriteFirebaseLogging);

In this situation alway the second write has sometimes a http status 400 error.
payloadstrings and path are definitily ok, a retry of the failure write works with no errors.

Now the wondering things:
First Point:
If I change only one of the 3 write commands to syncronous wirte i.e.

bool res= Database.set<object_t>(aClient, StatusPath.c_str(), object_t(jsonStatuspaylod.raw()));
if (!res)
      printError...
Database.set<object_t>(aClient, DayPath.c_str(), object_t(jsonDaypayload.raw()),processDataDay,"WriteFirebaseDay);
Database.set<object_t>(aClient, LoggingPath.c_str(), object_t(jsonLoggingpayload.raw()),processDataLogging,"WriteFirebaseLogging);

then everything works fine and i never got http status 400 error

Second Point
If I use WiFiClientSecure instead of ESP_SSSLClient (like you do in all your examples) then I didn't get any http statius 400 error also if I write to 3 realtimedatabase nodes asynchronous directly behind each other
Everything works fine without any errors.

This occurs on different hardware (Standard ESP32 devkit and ESP32-S3 devkit C-1 N16R8), I only use the native devkit board without addidional hardware powered by usb from my laptop, with very good wifi connection

I use latest platform version and latest version of FirebaseClient and ESP_SSLClient library.

What could be the reason for this behavior ?
What is different in ESP_SSLClient between asynchonous and synchronous write that can cause this behavior ?
Any help or answer is helpful and thanks for your excellent support in forward

[JoergTiedemann]

Any suggestions how to find the reason for the described behavior?