Mine was doing the same thing, the Velcro disks that screw in to the floor had worn out. I got a new set from Suncoast for around $25, 2 per side for a total of 4. I don't recall the part number. If they still have any of the clearance 987 mats at Suncoast, those come with a new set of the Velcro disk and are actually cheaper than buying the disks by themselves.
http://www.****************************************************.com/product/98704480000R10.html
The mats don't fit the 986 but it is a super cheap way to get 4 of the disks and you can use the mats around the house for something
