I suspect that the issue relates to the EASA
Safety Information Notice 2008-29 Anti-Icing.
The BAe146 / Avro RJ have similar servo-tab control systems to those in the MD. These aircraft use (used) a specific control check to aid de-icing fluid drainage, the tabs and control surfaces have an assortment of drain holes to minimize fluid buildup.
Fokker issued a service letter 50/60 Revision 2, Feb 28/07 on similar issues.
Anti-Icing Fluid Residues.
Flight Control Restrictions Due to Deicing/Anti-icing Fluid Residues.
Ongoing work "Deicing/antiicing fluids"
Deicing/antiicing fluids.
Deicing/antiicing fluid residues.