Some issues have "Issue Security Level" applied and The viewer does not have Browse Projects permission for some of the included projects are correct.

Some issues have "Issue Security Level" applied is correct because issue security schemes limit who can view individual issues even when those issues match the board filter. An issue with a security level that excludes the viewer will not appear on the board for that person.

The viewer does not have Browse Projects permission for some of the included projects is correct because a user must have Browse Projects permission on each project that the board includes in order to see that project’s issues. If the viewer lacks that permission for some projects then those projects’ issues will be hidden from them on the shared Kanban board.

A saved filter or the board subfilter excludes the missing issues is not the best answer in this scenario because although filters and subfilters can exclude issues they would not explain issues disappearing for some viewers while remaining visible to others. The question points to visibility restrictions that affect users differently so permissions and security levels are the likelier causes.

A work in progress limit is set on a board column is incorrect because work in progress limits control how many issues can be placed in a column and they do not remove issues from the board. A WIP limit will not cause issues to be missing from the board view.

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