Try to load xrns made with 2.7.2 in 2.8b5. Track with Pentagon 1 VSTi sounds different. Made clean project with one pattern and check it with both versions - result the same (various durations).
Attached XRNS and two mp3 rendered with various versions. Check also in 2.8b4 - sounds like 2.7.2
Windows XP SP3 32 bit.
Sorry, it’s look like no bug. The problem depends on audio driver sample rate. I don’t know why, but Renoise (both versions 2.7.2 and 2.8) produces the different note length in Pentagon on different sample rates.
I think that bug might be solved in the next version if that plugin depends on the same treatment as PianoTeq requires for changing samplerates:
http://www.renoise.com/board/index.php?/topic/33413-fixed-pianoteq-vst-does-not-pick-up-new-sample-rates/page__pid__262290#entry262290
I found this behavior may be partially ‘fixed’ in Pentagon1 by “2X oversampling ON” mode. Anyway it’s works the same way in previous versions of Renoise.
If you would have used the plugin bridged, i could perhaps find some logic for this action (64-bit processing so perhaps 2x oversampling required to double the 32-bit intensity), but you mention using Windows XP 32 bit so that renders my theory as utter cow-dung.