You'll be best served to wait until someone responds that actually knows what they are talking about, but I'll give you what I consider my "MIRACLE CURE" advice that always comes to mind when there is an issue regarding dash light issues. It may even work in your case.
Check the grounds and make sure both sides are well grounded.
(I assume same size/watt bulbs on each side.)
Again, someone else will have a better answer, but I was amazed at all the things in the dash that the correct ground solved for me.
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