After numerous crashes and an altogether laggy experience of koreader I remembered the extra lines cgm999 put in his koreader_kobo.sh script, which is situated in the main koreader directory.
The result is as of yet astounding:
- Koreader pdf pageturns are snappy again,
- it changes pdf from landscape to portrait and back without a hitch.
The changes to koreader_kobo.sh the following added lines:
# Decrease the reasons for crashes. Search forum for cgm999's explanation.
exec 3<&-
# Stop nickel and related processes
killall nickel
killall adobehost
killall dbus-daemon
killall hindenburg
Just copy-paste those lines after the first line (#!/bin.sh) and before the call to reader (# finally call reader).