If nothing was unclear or difficult, say so. Skip questions about steps you did not experience; use not applicable where appropriate.

Which invitation route brought you to this questionnaire?
What recent experience are you using to answer the feedback question?
Does the stated time period match that experience?
Which part of this invitation differs from the one you saw previously, if any?

Author notes / illustrative keys where applicable:
1. Use a non-identifying route description to inspect cohort composition.
2. Check whether waves refer to comparable experience rather than merely identical wording.
3. Find period mismatch that can change which experience is reported.
4. Probe invitation context without requiring someone to have answered an earlier wave.