check your ground
I used to have a small caravan that had similar issues with the lighting as it often sat unused for long periods and it seemed every time I hooked it up it had a blinking all over the place issue. I think it had a grounding issue built in because of the alluminium body, wood floor, steel chassi combination and build, perhaps different metal corrosion, reacting or something, I never got to the bottom of it However what usually repaired it was a good spray of WD40 or CRC into the plugs, light bulbs and or a tweek and spray on the ground wires bolts either at the lights themselves and/or on the chassi ground. Good luck
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