Bug with Koreader (& Coolreader) on Kindle PW2

I want to invert the colors on my Kindle PW2 for night reading mode and I have installed Koreader which allows this.

Unfortunately there is a bug in both Koreader and Coolreader on Kindle PW2 where about every 1000 words, give or take 200, there are a few letters, words or even whole sentences missing from the end of the paragraph. The missing sections come very regularly and it means that the book is unreadable. It doesn't seem to matter what format the ebook is in and the full file contents display perfectly in Calibre as well as the native Kindle reader - it is not a problem with the ebook file.

The location of the missing sections are identical for both Koreader and Coolreader. The segment section sizes are not too large to render and this issue occurs multiple times in each segment.

Does anyone have any experience with this or could someone point me in the right direction as to what in the Koreader/Coolreader engines is cutting off text at the end of paragraphs at regular intervals?

I am using the koreader-kindle-arm-linux-gnueabi-v2013.03-967-gb17b780 build.
Thanks