The shutter works on all speeds but is quite slow in the 1/2 - 1 second range. How can I get these shutter speeds happy?
If you can dismantle the front of the camera and access the shutter blades you can try the "lighter fuel" treatment (Graflex owners have been using this trick for long time). What you do is squirt a few drops of lighter fuel on the bladew and mechanism and operate the shutter a few times. It should work OK at the lower speeds. Then let it dry and using a toothpick oil the pins and springs. Use machine oil (sewing machine oil is very good) and only use minute amounts.

One word of warning though. If you do not feel confident about this do not attempt it. Better sent the camera for a proper CLA