Okay quick update time guys, as I've opened her up and had a good long nose around inside without finding anything wrong.
The PDI sears are both fine without any wear.
The Laylax red piston is also wear free.
No rubbing marks or little metal (or even plastic for that matter) shards flown around...
As Vindi says its prob' the 45degree angle giving me grief.
Ho-humm... *shrugs*