My hope is that my experiences with various customer service departments might help others: Of course none of us really has a large enough sample to mean a vendor is entirely good or entirely bad.
NiceHCK – Multiple orders, 1 bad cable, replaced after 1st contact without any questions.
Penon Audio – Multiple orders, 1 bad cable, replaced after 1 contact without any questions.
WooEasy – multiple orders – never a problem with any of them
AK Audio – multiple orders – never a problem with any of them
LunaShops – two orders – 1 bad cable, asked to prove it was bad and return it at my cost before a replacement would be sent. (Replacement cost elsewhere was less than return shipping)
KZ Store – multiple orders – one bad iem, asked to send photo of IEM iwth cable cut to prove destruction, item replaced after photo sent.
RUKZ Store – single order – no issues
AV Pro Store – multiple orders – no issues with any of them.
GearBest – multiple orders before conversion to ali like store – always good service, after conversion to ali style store, service is now hit or miss and responses to messages much slower than previously.
FastTech – multiple orders with no issues.
Better Audio (Amazon Store) – multiple orders, no issues
Kinboofi (Amazon Store) – multiple orders, no issues. (Fast responses to messages via facebook messenger).