[tomsem]

Seems like KOReader is having an issue.

I just installed it a couple of days ago, but I think if you last used KOReader to open a book, then KOReader becomes the default reading app for that book for single tap. If you never opened it with KOReader, then it'll use the default of PB Reader app. Long press lets you change this default. This would explain why single tap behavior varies from book to book.

You can launch KOReader from Apps screen by tapping on @koreader. Assuming that launches KOReader, you can then tap on settings ('gear' icon) and if you see Updates tap on that and you can Check for updates to see if that fixes its issue. Or it may be that this Updates feature has been added since you installed it, in which case you'd need to get the latest from GitHub.

I don't know what the difference is between ePub 2 and ePub 3 mode. I assume it uses ePub 3 by default, and ePub 2 is a fallback.

I'm still on the fence about KOReader. It's a little too bare metal for my tastes, and I'm having a few issues with it. PB reader is fine for the most part, and I like having TTS.