It could be your ammeter is inaccurate.
Inside the sun visor courtesy light is a 1.2W festoon bulb, that will draw ~0.1A ( which is near enough 0.09A.)
(Or try a 3W interior light bulb at 3W ~0.25A)
To check your ammeter is accurate, measure the current flowing through that bulb.
What meter current range gave you that reading of 0.09A ? Was it 0.2A ? 0.3A ? 2A ? 10A ? 20A ?
It may be the battery that is at fault. I believe that 20 near complete discharges is all it takes to destroy a car battery.
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