If there is an overlap of a trimming line, it is possible to have distorted mesh after trimming. Double check the trim curve and make sure there is no overlap of the trimming curve.
Use a smaller value of tolerance (TCTOL in
*DEFINE_CURVE_TRIM) for trimming. However, this may lead to small elements which may cause trouble in any subsequent analysis.
It is better to have a homogeneous mesh around the trimming curve, accordingly, it is better to trim the blank before coarsening the mesh. After coarsening the mesh, the size of the mesh might not be as homogeneous as before, and the chance of having bad elements increases when it is trimmed.