https://bugs.winehq.org/show_bug.cgi?id=42412
--- Comment #10 from Bruno Jesus 00cpxxx@gmail.com --- Thanks for the log, the one in comment 6 was what I was expecting. This is my only theory (aka wild guess) extracted from the slirp log+wine log+WinUAE sources:
WinUAE is caching all data read from the outside socket and delivering it to Amiga, but when the outside connection is closed WinUAE breaks the Amiga connection too instead of feeding it with the remaining cache before closing the Amiga connection. That means the final bytes of any transmission may randomly fail to be received depending on how fast the external connection is receiving and how fast Amiga is reading.