I have been flying a borrowed DJI Mini 2 on a few projects. It has worked great, so I finally bought my own. Out of the box, the front left motor doesn't spin. I could return it to the retailer or to DJI (leaning this way). However, I was wondering if there are any diagnostics I can run to possibly resolve the issue before wasting the time to send it back. Any common engine issues? I have worked in the electronics industry for decades, so I am confirmable with my own repairs.

May not be the motor itself as it could be a solder turned loose.  Not worth losing warranty replacement on a DIY repair.  Best to return it to the retailer where you bought it.  

Hello there Agentilis. I am sorry to read and to know about this issue with your new DJI Mini 2 and thank you for giving out these information. Since we are having issues with one of the motors of your of your DJI Mini 2.  It would be best to contact our DJI Support Team at https://www.dji.com/support?site=brandsite&from=nav for further assistance with regards to this matter. We will do our best to help you and give out the best resolution for the said issue. Just a friendly reminder that  DJI do not recommend doing a DIY in fixing the issue to avoid damaging the unit and for not to void the warranty of your DJI Mini 2 as well. Thank you.