A quick look at the PCB design and shutter position leads me to the following comments:
1. The likely greatest sources of heat in the SEEK are the switching regulator transistor and the microprocessor. If we treat them as warm air generators within the SEEK's sealed case and consider convection air movement we may find our problem.
2. From my brief view of the PCB the shutter operates from the top of the SEEK module where hot air will collect over time. This could warm up quite quickly as the micro will be a decent source of heat.
3. There is a large through-hole under part of the shutter arm and flag. The hole could potentially provide a focussed warm air path from the rear of the PCB to the front. The micro is on the rear so it is not unreasonable to think that the rear of the SEEK module will be warmer than the front in terms of air flow.
If I am correct, the air around the micro will warm up quicker than that around the lens assembly and this air will rise to the top of the module where it will find a path to the lens assembly via the through hole. Such a warmer air current is not great for the FFC shutter temperature gradient across the flags surface as it is in the path of said air current..
4. Proof of the theory would involve opening the camera shell and blocking the through hole in the PCB adjacent to the lens.
Additional thought....
Operating the SEEK without its rear shell in place would also stop the warm air build up that drives the air current through the hole and onto the shutter. This would prove the issue id thermal convection heating of the shutter flag rather than direct radiant heat from another heat source.
All this is coming from a pretty tired brain in the UK so forgive me if I have rambled on a bit !
EDIT,
I have added a picture taken by Marshall to help show the issue with the through hole above the lens assembly. (Hope this is OK with you Marshall)
Aurora