I got 3 pieces and ALL of them work 100% so Not sure if it is a process problem or an improper Handling issue. Static electricity and improper handling could also be the problem, User or Packaging , it is kinda lite. Are those bags anti-static I wonder. 
Honestly though I have purchase over 15 pcs. ALL XIAO line , BLE, SENSE and ESP32C and have not received a defective product yet from SEEEDStudio. I find it hard to believe with such a track record and no real revisions it can’t be a fab issue. IMHO… statistically I bet fails are less than .001% if they even keep track of this of MTBF. idunno?
HTH
GL 
I love the footprint and the capabilities, until I see a systemic failures I’ll keep using them all.
I’m looking forward to getting some LORA units next. try to push the range of Operation OUT even more.
Works like a BIG dog
but is Tiny like a Fly. 
ps. as far a support goes , well I’m pretty sure it’s only one person (requires a little patients) and they try to do a good job **
** but SEEED makes a crap ton of products. too many maybe. 