Fix of the issue is now available in InDesign’s latest November’17 update.
Please upgrade to the latest version InDesign CC 13.0.1 for the fix.
If you are unable to see the update, go to Creative Cloud application and click on the context menu on the top right and click on Check for App Updates.
InDesign TeamAnonymous commented
eyedropper tool won't sample text attributes correctly. My highlighted text turns invisible when I sample another word, and if I color it so I can see it it's still the same text as before I sampled. SUPER ANNOYING! May as well use Illustrator if I want to manually set text! I've double-clicked the eyedropper and everything is selected and I updated my InDesign last night. STILL HAPPENS! HELP! LOTS OF TEXT TO SET!