[arduino as isp]strange error message

hello,
I use a arduino mega 2560 as isp programmer to get a new bootloader on an arduino pro mini. Than I use the arduino mega as programmer to program the mini. On ide it is adjusted to do so and the target is adjusted as mini with 5v, 168, 16mhz. now it works up to one minute but than it breaks with this error message:

Arduino: 1.8.5 (Windows 7), Board: "Arduino Pro or Pro Mini, ATmega168 (5V, 16 MHz)"

avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x78
avrdude: stk500_getsync() attempt 2 of 10: not in sync: resp=0x78
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 3 of 10: not in sync: resp=0x78
avrdude: stk500_getsync() attempt 4 of 10: not in sync: resp=0x78
avrdude: stk500_getsync() attempt 5 of 10: not in sync: resp=0x78
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 6 of 10: not in sync: resp=0x78
avrdude: stk500_getsync() attempt 7 of 10: not in sync: resp=0x78
avrdude: stk500_getsync() attempt 8 of 10: not in sync: resp=0x78
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 9 of 10: not in sync: resp=0x78
avrdude: stk500_getsync() attempt 10 of 10: not in sync: resp=0x78
Fehler beim Brennen des Bootloaders.

It is in german but I think you can see enough. The problem I can't understand is:

It is adjusted to work with the mega as isp and where comes this stupid error message for stk500 from? Since this is not adjusted or setup this error message is not any part the ide can use to create the error message so where it comes from?

I tried to ask in german but the group there works more on how the question was asked as what the problem was. Four pages and no one was able to show where this software can get this error message since stk500 is not used anymore (programmer is arduino as isp). So any message in the ide it only can produce because it is programmed in and so I can not understand this.

Can anyone help me to adjust the ide correctly to program the bootloader not in the chip anymore?

I use the all of the description and all teh time only the green led on the mega is flashing slowly. reset of the chip is port 53 and the others are in 50-52. + and - is connected correctly. The led on the mini shows this.

greetings

manni