I do not know how to describe the problems exactly, but I'll try. (I apologize for my English)
When you split a sound clip into parts - the next time you play, in some joints can be heard audibly click, which should not be. The situation depends more on the location in which the splitting was than the time and other factors. In the system there is no xruns. When playing material recorded without splitting sound is excellent.
Clicks occur in a regular manner. Where they are - they are always the same every time you play.
The "time stretching" by SHIFT-dragging mode something is not working on audio clips.
The problem manifests itself in the mode "rubberband".
The point of it is that - when I split in a few places the clip, and try to adjust the rhythm (to correct vocal tempo inaccuracies) by moving the joints (through a "shift-dragging" by the edges) - instead of the expected change in the length, the content of the sound clip unimaginable way changing. Content of parts are jumps and changes its position in time quite differently than expected - in some unpredictable manner. It is hard to explain, but it sounds awful.
I tried to change the recording mode - 24 bit signed, 32 floating, all uncompressed, but the result is the same.
My system: Arch Linux x86_64 updated to the present day, qtractor-0.5.6 from the official repository, and qtractor-0.5.7 from sources (perfoms the same manner).