negative cell volume detected in dynamic meshing
 

Hi I am simulating flow in a 2D channel. the upper wall of the channel is intended to deform sinusoidally. I have used a UDF for this purpose. After setting the dynamic meshing (smoothing and remeshing). when I try to run the solution it gives an error of dynamic mesh update failed; negative cell volume detected.
anyone who can kindly tell me the reason for this. I have taken the wall as user defined(according to the UDF) and interior zone as deforming.
kindly refer to the attached image.
thanks