The best way to handle USB-CF under OpenBSD is to insert in the flash disk into the adapter first, then plug the USB adapter into the USB port on your computer. When you are done using the flash disk on the computer, unplug the USB adapter from the computer first, then remove the flash disk from the USB adapter. Follow this procedure every time and you will save yourself from hardship. Today, some kernel drivers are simply not aware of the reality of media that can be removed while the host adapter is still attached. Luckily, the USB host adapter drivers themselves are fully aware that the entire USB device can disappear.