Mechnical contacts can be tricky with small signals. A good low ohm contact may need a certain minimum current to flow.
The switch could well be OK for other uses (e.g. to switch a light or possibly even mains).
X2. The OP should look up the term "sealing current" or "wetting current". I found out about this early in my career when I tried to use a normal AC switch in a low current digital circuit. A digital rated switch was about 3x the price but it worked and a standard switch simply wouldn't, even when brand new.
Also on those Chinese made switches it very likely that the contacts were made of steel and had a very thin layer of tin on them and that the plating wore through very quickly. I've found that to be VERY common in cheaply made wire, bulbs, sockets, switches, etc.