The lamp could not work well for several reasons,either the lamp is not seated in the socket properly and firmly, or the lamp can be defective.And also the ballast may be defective. You can swap the ballast on each side to make sure which part is defective.This may be a magentic core/coil type transformer, or it may be a small box with electronic parts inside.
A loose wire at the lamp socket or the ballast will also cause a lamp no work.
Cold will cause to flicker or flash, either, in the unlikely event the light is subjected to a cold atmosphere.
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