Hello Edward,
It is a case of 'you get what you pay for'. I have 2 C/Y to Olympus 4/3 adapters. One I bought from a shop in New York, made by them, for about $135 if memory serves. It has taken some of the heaviest of lens combinations: Zeiss 300 + Mirotar II and remained solidly in place on the E-1. It also continues to perform flawlessly - lenses slide and lock perfectly, etc. I then bought a cheap version on ebay made in China - after 3 months, the 'stainless steel' ring is showing signs of corrosion, the machining of the screw holes was poor to start with and the assembly has slightly loosened. It arrived here in the UK in double-quick time but I would only use it in emergency and with the lens on a tripod.
On ebay, there is often a series of adapters made by a Japanese company (sorry, I can't remember the name but the listing names them specifically) for Canon EOS, Olympus 4/3 - they have a Buy It Now price typically of $150 or so - they are good.
Kind regards,
Graham