"No, when you receive a bad CRC, request a re-transmission."
That is when a bad CRC is received but what if packets are just dropped due to excess traffic somewhere?
The ESP32 should have a way to detect a timeout when acknowledgement of packet received by the FTP Server do not arrive back and would send the same packet again but it does not seem to be working this way.
And also, I am assuming packets are been dropped, I do not know if this is the case.