Mega transmits two junk characters upon opening serial connection without reset

Hi,

Whenever I open the serial connection to a Mega 2560 R3 without reset, it sends out two junk characters (plus CR). In HEX, it is: F0 F0 0D.
This happens with any program running on it, also the SerialEcho example.

The port is opened from Python-code and the reset is suppress by disabling the DTR. With Bray's Terminal, opening the port the same way, these junk characters also appear.
I also tried it with a 122 Ohm resistor between 5V and GND, bu this does not suppress the reset.

The code to open the port without reset:

ser = serial.Serial()
ser.port = 'COM8'
ser.baudrate = 115200
ser.timeout = 0.05
ser.dsrdtr = False
ser.setDTR(False)
ser.open()

This happens on two official Mega 2560 R3's with the 16U2 chip. On two replicate Nano's with CH340 chip everything works fine without reset.

Why are these characters sent? And can I suppress them?
Yes, I can ignore them of course, but I'd rather have a clean solution. Mostly because sometimes it only sends one char without CR, so it becomes a mess.

Thanks in advance for any help!

The port is opened from Python-code and the reset is suppress by disabling the DTR.

The Mega doesn't understand DTREnable. Only the 32U4 devices, like the Leonardo do. Unless you are physically preventing the reset, by cutting traces or adding capacitors, a reset IS happening.

I know for sure the microprocessor does not reset this way; I have print-statements in the setup() to monitor it, and the LED also does not blink as it does with a reset.

Could it be that the UART chip still does, or attempts, a reset and with that, outputs some garble?