If you know it has the specified viscosity oil in it & its not fuel diluted, doesn't smell strongly of fuel, maybe consider changing the oil filter.
Daughter had the same oil pressure warning light at idle problem when against my advice she had me use the specified Fram oil filter on her Saturn 4banger.
Fixed the flickering oil pressure light at idle problem by changing to the specified Purolator oil filter.
SO, maybe consider beginning with a check of the oil filter on there now, or just change it to the specified Motorcraft, in case the one on there now has a problem, won't be more than $4 bucks for the filter & maybe 1/2 qt oil to fill it.
More thoughts for consideration, let us know what you find.
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