It seemed that the reason in WiFiClient.cpp code. Old version code different and work well (have no "*RxBuffer" instances).

I faced with strange problem - in old ver of libs HTTP server answer to browser very fast (about 20 request in sec). But with new libs (esptool 2.3.1 xtensa 5.2.0) basic example SimpleWiFiServer.ino answer and freze for some timeout. It seemed that client.stop() not kill connection and client.avalab...

Its a strange bug. newer version of esp tools led to problem with transaction for example in standart simplewifiserver.ino code! In old version all fine, but in last version client.stop() not end connection, then in second loop client.connected() = true, but client.available() = false... in this bra...