Calling for real insider tips on fixing the MacBook 12-inch

I have attempted to repair two 12-inch MacBooks, one 2015 and one 2016. Most recently a standard display assembly replacement. Now, I have two dead MacBooks.

I average about half-a-dozen Apple repairs a month, both laptops and desktops with a nearly 100% success rate (excluding liquid damage jobs, where it's more like 60%). I follow the same care and troubleshooting principles across my job, but these "12-inchers" are getting me. Twice now, I have turned once-running MacBooks into paperweights.

No power, sound, lights or signs of life after reassembly.

I have watch teardown vids and your guides, the latter which is rather lacking in the area of precautions. Can someone contribute to the topic of pitfalls, mistakes and unique things to avoid when fixing a 12-inch MacBook? I'd be less vague if I had any notion where I'm goofing.

How I wouldn't give my eye teeth (or is that iTeeth) fora real Technician's Guide, right now.