At one time, I experienced this exact same difficulity with a KLN89B.
The fix was two fold.
The present data card was removed, and the pins that connect to same inspected closely.
One was just slightly misaligned and as a result, was not making proper contact.
The faulty pin was straightened (carefully), and a new database card then inserted.
Proper function restored.
Don't know if this will work on the KLN90, but certainly worth a try, I would think.