Have you tried cleaning and lubricating the levers? I have saved many shifters by soaking the internals with GT85 and operating them on the bike. The old shimano grease gums them up. Worth a try.
Common fix for rsx/rx100/600 brifters. Lots of videos on YouTube too.
@Boscarn started
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Have you tried cleaning and lubricating the levers?
I have saved many shifters by soaking the internals with GT85 and operating them on the bike. The old shimano grease gums them up. Worth a try.