Are you using the mirror lock-up feature for this shot?
If not, it's possible the motion of the mirror in your camera is causing an initial vibration, resulting in the blurring of the
LEDs vacuum tubes. Try the same shot again, but using the mirror lock-up function of your camera.
Edit: New theory. I don't believe there are any LEDs in the image. There are at least 3 vacuum tubes visible (center, left, and far left (mostly cropped)). The red glow at their bases is characteristic of valve operation. I believe the brightest red glow at the upper right is also the base of a tube.
I assume this is a tube amp, perhaps an amplifier head for an audio system or guitar amp. If the long exposure is being taken while the amp is driving speakers loudly, then there could certainly be some audio vibration of the amp, the camera, or both during the exposure.
You said the amp is on a table, and the camera is on a tripod. What are the table and the tripod on? If they are on a joist floor, or stage, it's entirely possible the floor is vibrating. Depending on how everything is set up, floor vibrations could cause the amp, or camera, to have forward/backward motion.
Even somebody just walking across a joist floor or stage could cause enough jolt to be visible in a long exposure image.