I'm including a small XNRS demonstrating the problem.
I've only tested this on 3.1.0.
I noticed this when a glide made a note louder, but I think something else might be going on with multiple volume samples and adjusting volume.
The instrument here was generated by Renoise's render plugin to instrument feature.
Edited by taktik, 04 March 2016 - 15:18.