Some Notes Cut Off???

I have a project that plays all the notes perfectly in Reaper but when I render it some notes are cut off prematurely. What am I doing wrong??? Thank you in advance for any and all assistance in this matter. Sean

In option/preferences/VST, make sure you have ''inform plug-ins of offline rendering state'' checked. What vsti is it ?

That seems to have done the trick. Thanks for the assistance. And to answer your question, I am using Kontakt 4 with an assortment of sample libraries. Again my thanks, Sean