While tried to screw J2 Motor Mount on J2 Motor. I was having problem to screw all 4 screws on and the holes was disalignm to J5 Motor screw holes. https://drive.google.com/open?id=1Z_nCLpG018-28HbPJdh_bXN2dxL9KZTY I have to grind it manually.

When performed first test run of AR2, suddenly J2 motor did not move and It appeared as the gear is disconnect with "crack crack" sound. Below is the video link to show the problem where gear is not turn when motor is on. https://drive.google.com/open?id=1j9uHmCQJbXa_a6Hua-s0aS3uwqeXK1NA Spending couple of days via email with OMC technician to trouble shoot and root cause finding. The technician concluded that the M6x20 cap screw is causing gearbox deformation which might be irreversible. Below is the photo what OMC technician email me:- https://drive.google.com/open?id=1JEy1Y1HE6WUywVh0ybPT5_8eqZEKMQWr I decided to change the way J2 Nema23 motor screw on J2 Motor Support. Below is the photo example:- https://drive.google.com/open?id=1wz636eNQobWJW6JIxhmENsC_CdGa6iAU By using 4 M4 cap screw and washer between J2 Motor Support and J1 Platform. AR2 has been running 6 hours (yesterday) and 4 hours (today, now still running) without J2 motor gearbox problem, I will update if problem keep come back which J2 motor gearbox deformation already irreversible and have to replace with new one. M6X20 cap screw and locking might not needed in aluminium structure which original is for 3D printed.