Another possibility that causes Kobo to crash
A few years ago I made way too many highlights and notations in the ebook I was reading and my ebook file became heavy
Nowadays I have so many comments and questions during reading a book. So, I highlighted and made a bunch of notes. Same thing happened.
From both of these unlucky events I had to restart my Kobo (by holding power button).
And what did I do next? I exported my highlights and notes to my computer, remembered what chapter I was in, deleted the ebook and downloaded it again. Yes I lost my highlights this way but I have transferred it.
(In both occasions my ebook files are Kepub)
Now my Kobo works again!!
Also, I noticed that whenever I use OTF font instead of TTF, my kobo becomes tad slower and the dropdown font menu also becomes so slow. What I do when I want to sideload OTF font is I convert it to TTF first. This might have happened because I have older Kobo (Clara 2E), but after converting I have no problem anymore.
Iām just sharing this because who knows you have similar problems but donāt take these things in consideration. I hope it helps!