Hi,
This is just a harmless cosmetic problem; the images are always integrated completely, irrespective of the percentages shown. It is just the progress monitoring information what fails. Of course this bug will be fixed in the upcoming version 1.8.0 RC4 of PixInsight.
I did note, however, that this integrating pixel rows took significantly longer than in 1.7.
I haven't seen this problem in our tests. Anyway, we have had some performance issues in RC3, which may also affect ImageIntegration. All of these problems are now completely fixed in PixInsight 1.8.0 RC4, which will be released in a few days. Besides much more stable and reliable, version1.8.0 RC4 is faster than PI 1.7 in all of our tests.