Writing to a proprety that hasn't been declared is deprecated, unless the class uses the #[AllowDynamicProperties] attribute or defines __get()/__set(). RFC: https://wiki.php.net/rfc/deprecate_dynamic_properties
When the memory limit is restored during shutdown, we may still be using a lot of memory. Ignore the failure at that point and set it again after the MM is shut down, at which point memory usage should be at its lowest point.