I have a Delica that is quite a few years old. In the last month or so, it has become like my knees. Very stiff to open when before it was quite smooth. I sprayed it with a cleaner, ran it through hot soapy water and tried a few drops of CLP. Whatever - in the morning, it is so stiff. If you open it a few times, it loosens up but gets stiff again in a small amount of time. I supposed there may be some gook in there but it isn't one that you can take apart.
Ideas?