I recently bought GPO and am very pleased with my decision to get it over another sample library. The sound quality and control is fantastic! While working on a piece today in overture, though, I stumbled onto a bug that a quick forum search says hasn't been reported.
The double bass section (basses Sus+Short) seems to have a really bad loop on G3, G#3, and A3. It "reattacks" about 4 seconds in and every 5 after that in the loop. Is there a fix for this? I am relatively confident I have all the updated patches, but I apologize if this has already been covered.
Some of these "glitches" or re-attacks may be bow changes. As you know, a string player cannot play long, continuous notes without reaching the end of the bow and having to reverse. Some of the reversals are more prominent than others. The loops do try to take into account the natural bow changes while still creating as smooth a sound as possible. The reason you're getting it on three notes is that the same sample is "stretched" across these three keys - that's what keeps GPO small and memory efficient.
If you have, or decide to get, Kontakt 2 then the patch can be loaded into it and you could adjust the loop point to your liking. Maybe someone else would care to chime in on this. You might also try combining two of the players from the solo basses. The three players are derived from alternate samples of each instrument and do not share the same samples - you may be able to find a more suitable sound there. Hope this helps.