The image below shows a Harmony Sovereign H1260 dovetail. There is only a little glue at the bottom of the tail.
In the image below you can see a little shim way down in the socket. It is not well adhered to the side of the socket. A few minutes after this image a slight chisel push and the shim popped right out.
After freeing the extension, this neck was removed easily. Wiggle, wiggle and out.
This is typical of original condition Harmony Sovereign guitars to some degree, therefore they all need a reset.