Its not the limiter that is weak on an x300, mine are fine, just the door metal fails eventually and then the limiter fails too. I've replaced limiter on mine and used bigger spacers on the door body side and its fine now.
1997, 4.0 LWB X300 - Unlucky car but still a daily driver.
1988, 3.6S XJS - Never ending restoration project.
1994, 3.2S X300 - Accident damaged, October 2015. Gone!
1994, 3.2S XJ40 - Long gone.