Originally posted by Mike Cash
Not familiar with the Kood. If it is one of the models that has a flange covering the electrical contacts that would explain not asking for focal length. I use aluminum foil to cover the contacts and the same thing sometimes happens.
The Kood adapter looks like a direct copy of the Asahi adapter - when inserted it is flush with the flange, so the contacts touch the lens body. Since the body is painted the contacts are isolated. Which contacts do you cover with foil?
Originally posted by Mike Cash
I would guess that a small portion of the locking spring remains attached and protrudes just enough to cause it to catch on a bayonet lug. Try using a small pair of tweezers to compress the remaining portion of the spring down to the adapter body and rotate the adapter while still holding the spring remnants clamped down.
Oh, and you might want to do that last bit with the camera held "upside-down" (with the body opening facing the floor) so just in case something else breaks off gravity will work to reduce the chances of it falling into and damaging your mirror or focus screen.

Yes, you are right. After nervously rotating the adapter for a while I decided to use a bit more force. There was a 'ping' and the leaf spring fell out. Then after a bit more manipulation the adapter suddenly became loose and a small screw fell out.
I think that the spring was not properly screwed in and when I first attached the adapter the spring and screw jammed the adapter in place. Without the spring the adapter can now be attached and detached easily. However, one lens I have has a stiff focus ring and I have to be careful not to detach the adapter as I focus

. I'll keep a look out for a genuine Asahi Pentax adapter, perhaps that will work a bit better.