Problem uploading into Adafruit Feather M0

If this issue is out of scope on this forum, let me know and I will delete the topic.

When trying to load a sketch into Feather M0 getting an error: SAM-BA operation failed

details:
Windows 7 64,
Arduino 1.8.12 (also tried 1.8.2 and 1.8.0),
installed Arduino SAMD 32bit Cortex-M0 Boards 1.8.6,
Adafruit SAMD 32bit Cortex-M0 Boards 1.5.14
Also ran adafruit_drivers_2.3.4.0.exe

Trying to load Blink sketch , got message:
An error occurred while uploading the sketch.

Error in the output: SAM-BA operation failed

But it looks like sketch does upload, tried loading 'Blink', 'ASCII' and 'SD card test' from 'Examples' - still give the same error when uploading, but LED blinks, Serial communication works and SD content reads correctly.

Used 2 different Feather boards with the same result.
Used 2 different computers (both Windows7), same error.
Tried to run on WindosXP, failed (no board drivers available)
Tried to run Arduino IDE under admin privileges, same error.
Also tried connecting Arduino to USB2 or USB3, changed cable - same error.

Verbose output from IDE:

Sketch uses 10620 bytes (4%) of program storage space. Maximum is 262144 bytes.
Forcing reset using 1200bps open/close on port COM30
PORTS {COM30, } / {} => {}
PORTS {} / {} => {}
PORTS {} / {} => {}
PORTS {} / {COM32, } => {COM32, }
Found upload port: COM32
C:\Users\KD\AppData\Local\Arduino15\packages\arduino\tools\bossac\1.7.0-arduino3/bossac.exe -i -d --port=COM32 -U true -i -e -w -v C:\Users\KD\AppData\Local\Temp\arduino_build_509365/Blink.ino.bin -R
Set binary mode
readWord(addr=0)=0x20007ffc
readWord(addr=0xe000ed00)=0x410cc601
readWord(addr=0x41002018)=0x10010305
version()=v2.0 [Arduino:XYZ] Mar  5 2016 17:46:52
chipId=0x10010005
Connected at 921600 baud
readWord(addr=0)=0x20007ffc
readWord(addr=0xe000ed00)=0x410cc601
readWord(addr=0x41002018)=0x10010305
Atmel SMART device 0x10010005 found
write(addr=0x20004000,size=0x34)
writeWord(addr=0x20004030,value=0x10)
writeWord(addr=0x20004020,value=0x20008000)
Device       : ATSAMD21G18A
readWord(addr=0)=0x20007ffc
readWord(addr=0xe000ed00)=0x410cc601
readWord(addr=0x41002018)=0x10010305
Chip ID      : 10010005
version()=v2.0 [Arduino:XYZ] Mar  5 2016 17:46:52
Version      : v2.0 [Arduino:XYZ] Mar  5 2016 17:46:52
Address      : 8192
Pages        : 3968
Page Size    : 64 bytes
Total Size   : 248KB
Planes       : 1
Lock Regions : 16
Locked       : readWord(addr=0x41004020)=0xffff
readWord(addr=0x41004020)=0xffff
readWord(addr=0x41004020)=0xffff
readWord(addr=0x41004020)=0xffff
readWord(addr=0x41004020)=0xffff
readWord(addr=0x41004020)=0xffff
readWord(addr=0x41004020)=0xffff
readWord(addr=0x41004020)=0xffff
readWord(addr=0x41004020)=0xffff
readWord(addr=0x41004020)=0xffff
readWord(addr=0x41004020)=0xffff
readWord(addr=0x41004020)=0xffff
readWord(addr=0x41004020)=0xffff
readWord(addr=0x41004020)=0xffff
readWord(addr=0x41004020)=0xffff
readWord(addr=0x41004020)=0xffff
none
readWord(addr=0x41004018)=0
Security     : false
Boot Flash   : true
readWord(addr=0x40000834)=0x7000a
BOD          : true
readWord(addr=0x40000834)=0x7000a
BOR          : true
Arduino      : FAST_CHIP_ERASE
Arduino      : FAST_MULTI_PAGE_WRITE
Arduino      : CAN_CHECKSUM_MEMORY_BUFFER
Erase flash
chipErase(addr=0x2000)
done in 0.850 seconds

Write 10876 bytes to flash (170 pages)
write(addr=0x20005000,size=0x1000)
writeBuffer(scr_addr=0x20005000, dst_addr=0x2000, size=0x1000)

[===========                   ] 37% (64/170 pages)write(addr=0x20005000,size=0x1000)
writeBuffer(scr_addr=0x20005000, dst_addr=0x3000, size=0x1000)

SAM-BA operation failed
An error occurred while uploading the sketch

[======================        ] 75% (128/170 pages)write(addr=0x20005000,size=0xa80)
writeBuffer(scr_addr=0x20005000, dst_addr=0x4000, size=0xa80)

[==============================] 100% (170/170 pages)
done in 0.080 seconds

Verify 10876 bytes of flash with checksum.
checksumBuffer(start_addr=0x2000, size=0x1000) = 7383
checksumBuffer(start_addr=0x3000, size=0x1000) = be04
checksumBuffer(start_addr=0x4000, size=0xa7c) = 2889
Verify successful
done in 0.014 seconds
CPU reset.
readWord(addr=0)=0x20007ffc
readWord(addr=0xe000ed00)=0x410cc601
readWord(addr=0x41002018)=0x10010305
writeWord(addr=0xe000ed0c,value=0x5fa0004)