The following article is a summary article based on a forum discussion. Many thanks to Ian, Bill and others for the advice and photographs.
The mainsheet track systems fitted onto many SO37's, SO40's - including DS and some other models around 2000-2006 requires regular servicing to avoid salt corrosion and seizing of the alloy and stainless steel components that can lead to failure under load.
The alloy eye must be free to fully swivel on the stainless pin.
If your system is already seized and corroded it may be very difficult to remove the stainless pin from the car, but the following may help in making permanent repair.
To remove the car from the traveller there is a 5mm Allen key bolt that holds the end on - you will need to apply lots of lube to the bolt whilst working it in and out. Best to use quality T bar socket fitting with a long lever rather than short Allen keys. Slide the car off BUT when you slide the car off the traveller, about 50 ball bearings WILL fall out - so do it slowly and put a towel down to catch them all!!
If the Allen bolts are too seized you may need to be more destructive and drill the alloy swivel to remove it whilst it is still in-situ. The swivel had a brass bearing which will need to be removed as well.
If the pin in the traveller is seized solid try boiling it, adding more lube then giving firm taps with drift to crack the bond.
Make sure you drift it out from the opposite side to the splined end or you will groove the bearing.
Spare parts may be difficult to obtain and will be expensive, and the quality may still be poor so investigate having a machine shop fabricate a new toggle as shown in these photographs - it may be more cost effective than replacing the whole track system.
The forum discussion can be viewed HERE: