Not sure of the specifics on the top on the Sprinter body, but I would assume itís very similar to what they were doing on the E series.
Usually there was some fabric and foam placed in between the spring and the channels to help with any spring slap. There was also a process of tightening the spring tension on the manual lift tops, but not sure that is applicable to the electric lift mechanisms.
I would suggest you open things up by unscrewing and peeling the fabric back to expose the spring to see whatís going on, you might find thereís some spray adhesive also keeping things in place, get yourself a can of adhesive if needed when buttoning things back up. Place some thin foam and fabric in the channel under the spring, see if thereís a way to adjust the tension if needed.
'03 Ford E350 7.3L Diesel
(de)SMB'd Custom RB-50
Quigley 4X4 w/Deavers & Agile Offroad's R.I.P. package
CCV High Profile Pop Top