One motor suddenly stops mid air

After couple of minutes flying (3-4 mins) my one motor suddenly stops for few seconds, then starts to spin again. Luckily I saved it from crash and brought it back home safely. Also I noticed that when I arm the drone, the motor that stops mid air has hard time spinning. It’s stuttering even at full throttle.
Could it be esc problem?

Here is the logs:!QuRzjLyI!pXapFjo50Ls1xR1P70V1wZiJtZlAWzJd5ysVypRHnu8

Log File C:\Users\den\AppData\Local\Temp\tmp7AB0.tmp.log
Size (kb) 354.6044921875
No of lines 5609
Duration 0:00:00
Vehicletype ArduCopter
Firmware Version V3.2.1
Firmware Hash 36b405fb
Hardware Type
Free Mem 0
Skipped Lines 0
Test: Autotune = UNKNOWN - No ATUN log data
Test: Brownout = GOOD -
Test: Compass = GOOD - No MAG data, unable to test mag_field interference

Test: Dupe Log Data = GOOD -
Test: Empty = GOOD -
Test: Event/Failsafe = GOOD -
Test: GPS = FAIL - Min satellites: 0, Max HDop: 99.99
Test: IMU Mismatch = UNKNOWN - No IMU log data
Test: Motor Balance = UNKNOWN -
Test: NaNs = FAIL - Found NaN in GPS.VZ

Test: OpticalFlow = FAIL - ‘FLOW_FXSCALER’ not found
Test: Parameters = GOOD -
Test: PM = GOOD -
Test: Pitch/Roll = GOOD -
Test: Thrust = GOOD -
Test: VCC = WARN - VCC min/max diff 0.372v, should be <0.3v

Also my log time is very strange, it says 1970 2:00 am.

You’re using a very old version of ArduCopter.

Anyway, the symptoms you describe indicate a possible ESC or motor failure.

…or a bad connection such as a bullet connector.

Drove me mad finding that one.Solder them solid now.

Your log file has very little data.
I find RCout most telling but you are not logging that value.