fix: only apply instance-strip transformer to schema errors (via #5110)

src/core/plugins/err/error-transformers/transformers/strip-instance.js

@@ -1,7 +1,11 @@
 export function transform(errors) {
   return errors
     .map(err => {
-      return err.set("message", removeSubstring(err.get("message"), "instance."))
+      if(err.type === "schema") {
+        return err.set("message", removeSubstring(err.get("message"), "instance\\."))
+      } else {
+        return err
+      }
     })
 }