I think you're asking for a lot of testing, ie to see if equivalent parts from different manufacturers meet their specs or absolute limits.
I use all my components with quite conservative ratings so I don't have any particular failures to note, but I have used a few cheaper brands:
JSMSEMI - Discrete transistors, RS485 transceivers
HGSEMI - RS485 transceivers
UMW Youtai Semiconductor - Logic ICs, Darlington Arrays
SX Shenzhen Suosemi - DC/DC converters
XLSEMI - DC/DC converters
XINLUDA - Charge Pump ICs
Xiamen Faratronic - Film Capacitors
Everlight - LEDs, Optocouplers
Microdiode Electronics - Diodes
Micro Commercial Components - Diodes
Resistors - YAGEO, Chian Chia Electronic, Walter Electronic, Thunder Components, Resistor Today, Uni Royal, and more