Problem with optiboot sequence: data transfer needed before program sends 0x30?

Hello, thank you for your time reading my post:
I have been working on a custom build atmega328p board for some time.
It will be inserted into a device, that should be remotely administered via a one wire bus.
Data Transfer to and from device works fine.
Currently it is connected to a MEGA2650. The MEGA acts as my communications relay between my Serial-Monitor and the device when operated and should also act as a relay to my USB-FTDI-Programmer, when a new sketch needs to be uploaded / updated.

Setup:
MEGA Serial : Computer (Serial Monitor)
MEGA Serial1: to one-wire Chip - finally to device
MEGA Serial2: can be activated for testing upload to device via rx/tx
MEGA Serial3: USB-FTDI (the DTR-Pin is also relayed to the device via digital-Output of MEGA)

When the device (rx/tx) is connected with Serial2 the upload of a new sketch is allways succesfull, showing communication as follows:

Sorry for the decimals (48 = 0x30 / 32 = 0x20) these are the initializing bytes I allways read about during my research on the internet). The initial communication allways consists of two seemingly random values on which the device answeres by incrementing the first value by 3 and sending the second value back unchanged. (I am sorry, but I could not find out, what these represent)

Resettime: 8273 (milliseconds)
Out-Bytes: 58 8724 In-Bytes: 61 8946 ( I. :seemingly random value = answer incremented by 3)
Out-Bytes: 51 8944 In-Bytes: 51 8948 (II. : seemingly random value = answer unchanged)
Out-Bytes: 0 9475 In-Bytes: 0 9478
Out-Bytes: 0 9476 In-Bytes: 0 9479
Out-Bytes: 48 9990 In-Bytes: 20 9993
Out-Bytes: 32 9991 In-Bytes: 16 9994
Out-Bytes: 65 10010 In-Bytes: 20 10014
Out-Bytes: 128 10011 In-Bytes: 3 10015
Out-Bytes: 32 10012 In-Bytes: 16 10016
Out-Bytes: 65 10032 In-Bytes: 20 10036
Out-Bytes: 129 10033 In-Bytes: 8 10037
Out-Bytes: 32 10034 In-Bytes: 16 10038
Out-Bytes: 65 10047 In-Bytes: 20 10051
Out-Bytes: 130 10048 In-Bytes: 0 10052
Out-Bytes: 32 10049 In-Bytes: 16 10054
Out-Bytes: 65 10063 In-Bytes: 20 10067
Out-Bytes: 152 10064 In-Bytes: 3 10068
Out-Bytes: 32 10065 In-Bytes: 16 10070
Out-Bytes: 65 10080 In-Bytes: 20 10084
Out-Bytes: 32 13115 In-Bytes: 16 13119
...

When I try to upload the sketch via my one-wire connection, I get the following:

Resettime: 16486
Out-Bytes: 48 17064 In-Bytes: 20 17068
Out-Bytes: 32 17065 In-Bytes: 16 17069
Out-Bytes: 48 17596 In-Bytes: 0 0
Out-Bytes: 32 17597 In-Bytes: 0 0
Out-Bytes: 48 18111 In-Bytes: 0 0
Out-Bytes: 32 18112 In-Bytes: 0 0
Out-Bytes: 0 0 In-Bytes: 0 0
Out-Bytes: 0 0 In-Bytes: 0 0
Out-Bytes: 0 0 In-Bytes: 0 0
...

shows an error:
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0xe4

So response times to the 0x30 and 0x20 send by the progammer are answered as timely as with rx/tx connected. The error seems to be related to the sequence in I. and II. that is missing in the one-wire commuication.

What I desparately need is a hint to what theses lines acutally represent and how they are generated (i.e. timing of target chip reset / is there a "hidden" communication initialisation I missed by the target chip) ?

After several nights of extra work on this, I get a bit confused. So sorry, if the above sounds equaly confusing.

I appreciate any help on this!
Best regards

SOLVED!!!
My Bad! Or close! Compiled a corrupt bootloader that somehow had the flag set for "Disable external Reset".
Compiled new Bootloader - works like a charm.