Students are hesitant to ask questions or provide feedback to other students. Students can feel uncomfortable being critical of fellow students or can find it difficult to respond to new arguments on the fly.
Model questions and feedback. After allowing time for other students to respond first, raise questions or provide feedback to students yourself.
Provide example responses. Ahead of presentations, create some generic clarifying questions or points of constructive criticism exemplifying the kind of responses you expect, and share these with students at the start of section.
There is not enough time for all students to present. Even with short presentations, it can be difficult to find time for all students to present.
Reserve a section for presentations.
Break students into smaller groups and have them present to their groups