In my organization Scrum teams almost never finish all of their stories 100%.
I suggested that we commit to fewer stories each Sprint, but the R&D manager says if we do that people will still not complete the work, but will just do less of it thus slowing down development.
He says there is a Student Syndrome at work here.
From my limited experience with [what poses for] Agile, I'm not surprised.
Everything I've read about Agile suggests that everybody needs far more organised than in other development technique but, like you, I'm seeing little, if any, evidence of it.
Estimating Story Points is not an exact science, especially in "cutting-edge" areas like R&D. It could easily be that your Developers are mis-estimating their Story Points (IME, usually over-estimating their own abilities) or it might be that there's some "target" number of Points that they're supposed to produce in each Sprint (IMHO, an utterly flawed way to manage, which brings me to ...).
Your manager needs to be investigating this and finding out what's not working. It's their responsibility to get stuff delivered to the clients (or it ought to be), and so their "neck on the block" when the users start complaining.
[cynicism]Of course it won't be, because they have all the necessary training/ skills to make sure none of the blame sticks to them. [/cynicism]
And insulting their workers, branding them with any kind of "syndrome", is never acceptable behaviour - it just shows management's lack of commitment to the Team and their desire to "distance" themselves from it.
Development is being slowed down either way, but doing the job slowly and more conscientiously (i.e. actually making stuff work) is far, far better than simply not delivering anything at all.