diff --git a/editor/import/3d/post_import_plugin_skeleton_rest_fixer.cpp b/editor/import/3d/post_import_plugin_skeleton_rest_fixer.cpp
index 2e3e226c34..bcc315cd57 100644
--- a/editor/import/3d/post_import_plugin_skeleton_rest_fixer.cpp
+++ b/editor/import/3d/post_import_plugin_skeleton_rest_fixer.cpp
@@ -794,6 +794,14 @@ void PostImportPluginSkeletonRestFixer::internal_process(InternalImportCategory
 								Quaternion new_rest_q = new_rest.basis.get_rotation_quaternion();
 								Quaternion old_pg_q = old_pg.basis.get_rotation_quaternion();
 								Quaternion new_pg_q = new_pg.basis.get_rotation_quaternion();
+
+								// [TINQS] Diagnostic: log before/after for first key.
+								if (key_len > 0) {
+									Quaternion bq = static_cast<Quaternion>(anim->track_get_key_value(i, 0));
+									Quaternion aq = new_pg_q.inverse() * old_pg_q * bq * old_rest_q.inverse() * old_pg_q.inverse() * new_pg_q * new_rest_q;
+									WARN_PRINT("[TINQS] " + String(bn) + " before=(" + String::num(bq.x,2) + "," + String::num(bq.y,2) + "," + String::num(bq.z,2) + "," + String::num(bq.w,2) + ") after=(" + String::num(aq.x,2) + "," + String::num(aq.y,2) + "," + String::num(aq.z,2) + "," + String::num(aq.w,2) + ")");
+								}
+
 								for (int j = 0; j < key_len; j++) {
 									Quaternion qt = static_cast<Quaternion>(anim->track_get_key_value(i, j));
 									anim->track_set_key_value(i, j, new_pg_q.inverse() * old_pg_q * qt * old_rest_q.inverse() * old_pg_q.inverse() * new_pg_q * new_rest_q);