One specific epub dead slow in viewer?

[Claghorn]

I use the calibre from the fedora repos. Sometime in the last few months, an epub book that always opened just as fast as all my other epubs suddenly started taking forever to render in the viewer. The screen stays white for 10 or 15 minutes, the system monitor says 1 cpu is pegged at 100% and if I wait long enough, it finally shows up.

If I run strace while it is eating cpu, I see an infinite number of lines like this:

...
madvise(0x7f0dbe150000, 4096, MADV_NORMAL) = 0
madvise(0x7f0dd757c000, 8192, MADV_NORMAL) = 0
madvise(0x7f0dd757a000, 8192, MADV_NORMAL) = 0
madvise(0x7f0dd7024000, 16384, MADV_NORMAL) = 0
madvise(0x7f0dd701c000, 16384, MADV_NORMAL) = 0
...

The exact same epub opens with no problems on fbreader in my android tablet.

Is there any way to debug what is going on here? This is one of the many Discworld books I have, and as near as I can tell came from the same source as all the others which don't seem to have this problem.

Details:

calibre-3.1.1-1.fc26.x86_64
Eric - Terry Pratchett.epub

I bought all my Discworld books from either google or amazon and stripped the DRM so I didn't have to read each book in a different app.

[Claghorn]

OK, I experimented a bit. I converted the original epub to mobi, then converted the mobi back to epub, and the new epub displays fine, no huge delays. The new epub is also considerably smaller (but I don't notice anything missing when I read it):

orig versus epub->mobi->epub:

-rw-r--r-- 1 tom users 715135 Sep 2 19:39 Eric - Terry Pratchett.epub
-rw-r--r-- 1 tom users 191426 Sep 2 19:48 Eric - Terry Pratchett.epub

so I guess I have a work around even if I have no idea why the original book suddenly got so slow.

[JSWolf]

You really should try to find out why the ePub is acting up.