Well I test assemble them half way and that goes pretty easy with a wood sacrifice and hammer (if the joint is too tight I carefully file the pins). But it is more difficult with glue. I am positive that applying glue takes only 2 minutes. They enter fine but just after some mm it get stuck. I have to apply a lot pressure until a sharp click is heard and they enter a few mm. They immediately get stuck again and I have to build up pressure with the clamps. This has to be repeated 3-4 times and the last gap is very tough to close.
The drawers are of ash and some 20 mm (3/4") thick. I dilute the glu with some water to get it less thick.
I have made a lot of drawers but not experienced this problem before. The glue is 2-3 years old - could that be the problem?