Dear Kate,
I suspect this is not a bug, but the direct consequence of (mis)using a code-set "multiple user data entry" mode. Code-sets should be placed in "multiple user" mode only when you wish to conduct a double/multiple blind coding/screening round. "Single user" mode is safe for all other tasks. We are aware that the mode-names are somewhat misleading and are about to change them (we hope to include this change in the next update, hopefully in mid June).
In detail: the "multiple user data entry" mode is designed to allow double/multiple blind coding, so that two or more reviewers may be able to assign codes to the same items without seeing each other's decisions.
When a code-set is in "multiple user" mode, different things may happen as the result of applying a code to an item:
1) if the item has no codes from the set, or if the item has "uncompleted" codes, the new code will be assigned as "uncompleted" and will be visible to the person that added it only. Reporting/searching features of EPPI-Reviewer will not detect this coding.
2) if the item already has "completed" codes in the set, the new code will be added to the "completed" collection, and will be visible to all users (and appear in reports, frequencies tables, searches, etc).
I've given a look at your review, and some items have "completed" codings from the screening set, some other have uncompleted codes, mostly applied by Katherine. What I think happened is that you had some items already completed, "bulk assigning" selected items to a given code would work straight away from them. The same operation (select some items, right click on a code and "assign selected items to this code") to items that don't have any completed coding in that set would add the new codes as "uncomplete" (or private) and the other members of the review will not see them.
To solve this issue, you can bulk-complete the coding that was already added (if my "diagnosis" is correct!), this is done on the "Review Statistics" tab (low right on the main screen), you can expand the lines of uncompleted codes so to see to who they belong, and then click on the green "v" little button to complete them all in one go (on a per-person basis). This should make all your "disappeared" codes visible again. Once you have completed all the coding that you wish, you may want to switch the code set to "single user" once more, so to avoid having the same issue again.
I hope this helps,
Sergio