I can tell you that there are 4 rollers on my kitchen slide because of the marks on the floor.
Not sure, but my guess is you will need to unmount the box from the mechanics so you can tilt the outside down to raise the inside for access.
Can you look in the bottom of the cabinets to if there is a structural problem.
Sounds like a roller came off or broke apart.
There are USB cameras you can get on ebay for $13 which are small enough to fit under the floor of the slide box.
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