Occasionally, a crash occurs when attempting to free a CCW. The crash occurs in the "mono_marshal_free_ccw" function. It seems to be caused by an invalid pointer to the CCW list for an object returned from the ccw_hash hashtable. The CCW list pointer becomes invalid when the first item in a CCW list is removed. The hashtable holds the pointer to the first item in the list, so the pointer it holds becomes invalid in that case. The fix would be to re-add the CCW list to the hashtable when the first item in the list is removed.
Applied a fix to mono master a568b19c13fc2ea713f8ac2d9f2126214cae4ff7.