frastema 88/FA optometrist chair

hi everyone,

I am going to see the above chair, Frastema 88/FA chair, the issue is that the locking handle that keeps the chair in position or allows it to swivel then locked in the required position is not locking and the chair still moves. Taking the seat off, exposes the locking mechanism, i tightened the spindle, shown in the photo with the 3 holes, and that seemed to have resolved the issue, but the hospital rang it back in saying it still moved. Has anyone seen this before and is there anything else i need to tighten to stop the chair from moving?

regards,

PhilAttachment 14969