I appreciate the help, though I've looked inside my ports before and found neither dust nor lint. The problem seems to be mostly with cheaper stuff. I've mentioned this to USB-C enthusiasts before and gotten back, "Well, just by better-quality stuff." The difference is, I never had any problem with the connection on cheap USB-A devices. If the connector seemingly can't be made both cheaply and well, that is a huge flaw with the standard and means it ought to be abandoned wholesale.