Not sure if that's possible ; my kobo libra 2 just became slower after I updated metadata and created collections (based on calibre tags) . Can it be that it slowed things down that much? I've read collections can create issues and slow the device down , but I only got 15 of them (I only have 15 tags) 
https://imgur.com/a/HUcPz1J (video showing the slowdown) 
Or did something get corrupted ? I wanted collections but I kind of regret it since the experience is now more ... sluggish 
(Unless I'm crazy and it isn't actually slower, what do you think objectively?)