Problem with the verification during programming with a new batch of chips/board

Hi, I have a custom board that had a previous production batch and that worked without any problem. They are using the internal oscillator at 8MHz and the optiboot (specifically the DualOptiboot 5.0 used with Moteino), that is tunned for using the internal 8MHz oscillator. All of this worked fine with the first set of boards that were manufactured. Now I have a new set of boards, and some of them have problems in the verification phase at the end of the programming, like this:

C:\Work\arduino-1.6.8\hardware\tools\avr/bin/avrdude -CC:\Work\arduino-1.6.8\portable\packages\Moteino\hardware\avr\1.3.0/avrdude.conf -v -patmega328p -carduino -PCOM16 -b57600 -D -Uflash:w:C:\Users\Fernando\AppData\Local\Temp\build7652e8c1a7fea338fa38d2ee03cb258c.tmp/PropaneSensor2Tx.ino.hex:i

avrdude: Version 6.0.1, compiled on Apr 15 2015 at 19:59:58
Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
Copyright (c) 2007-2009 Joerg Wunsch

System wide configuration file is "C:\Work\arduino-1.6.8\portable\packages\Moteino\hardware\avr\1.3.0/avrdude.conf"

Using Port : COM16
Using Programmer : arduino
Overriding Baud Rate : 57600
AVR Part : ATmega328P
Chip Erase delay : 9000 us
PAGEL : PD7
BS2 : PC2
RESET disposition : dedicated
RETRY pulse : SCK
serial program mode : yes
parallel program mode : yes
Timeout : 200
StabDelay : 100
CmdexeDelay : 25
SyncLoops : 32
ByteDelay : 0
PollIndex : 3
PollValue : 0x53
Memory Detail :

Block Poll Page Polled
Memory Type Mode Delay Size Indx Paged Size Size #Pages MinW MaxW ReadBack


eeprom 65 20 4 0 no 1024 4 0 3600 3600 0xff 0xff
flash 65 6 128 0 yes 32768 128 256 4500 4500 0xff 0xff
lfuse 0 0 0 0 no 1 0 0 4500 4500 0x00 0x00
hfuse 0 0 0 0 no 1 0 0 4500 4500 0x00 0x00
efuse 0 0 0 0 no 1 0 0 4500 4500 0x00 0x00
lock 0 0 0 0 no 1 0 0 4500 4500 0x00 0x00
calibration 0 0 0 0 no 1 0 0 0 0 0x00 0x00
signature 0 0 0 0 no 3 0 0 0 0 0x00 0x00

Programmer Type : Arduino
Description : Arduino
Hardware Version: 3
Firmware Version: 5.0
Vtarget : 0.3 V
Varef : 0.3 V
Oscillator : 28.800 kHz
SCK period : 3.3 us

avrdude: AVR device initialized and ready to accept instructions

Reading | ################################################## | 100% 0.00s

avrdude: Device signature = 0x1e950f
avrdude: reading input file "C:\Users\Fernando\AppData\Local\Temp\build7652e8c1a7fea338fa38d2ee03cb258c.tmp/PropaneSensor2Tx.ino.hex"
avrdude: writing flash (17108 bytes):

Writing | ################################################## | 100% 6.43s

avrdude: 17108 bytes of flash written
avrdude: verifying flash memory against C:\Users\Fernando\AppData\Local\Temp\build7652e8c1a7fea338fa38d2ee03cb258c.tmp/PropaneSensor2Tx.ino.hex:
avrdude: load data flash data from input file C:\Users\Fernando\AppData\Local\Temp\build7652e8c1a7fea338fa38d2ee03cb258c.tmp/PropaneSensor2Tx.ino.hex:
avrdude: input file C:\Users\Fernando\AppData\Local\Temp\build7652e8c1a7fea338fa38d2ee03cb258c.tmp/PropaneSensor2Tx.ino.hex contains 17108 bytes
avrdude: reading on-chip flash data:

Reading |
avrdude: stk500_paged_load(): (a) protocol error, expect=0x10, resp=0x0a
avrdude: stk500_cmd(): programmer is out of sync

I've noticed that the chip marking is different but I think that it has to do with Atmel beeing now Microchip, there are notices for the modification, nevertheless I'm attaching photos of both chips, old and new.

I've noticed also that with the previous batch I could use the serial port at 115200 (I know that it is over the spec when using the internal 8MHz oscillator, but it worked), and with the new batch of chips I have lots of bytes corrupted on the serial port, this I think is due to some oscillator deviation, and it works if I reduce the bitrate to 57600.

What do you think the problem could be?

Best regards

Fernando