well, I would say if you start excluding some comp, then you have, in effect, while you haven't suspended it, you have reduced the safe harbor during the year. The IRS has the following comments in regards to that:
Some changes, such as reduction or suspension of safe harbor contributions, adding or dropping safe harbor status, or changes in plan years, are permitted only as described in existing regulations
https://www.irs.gov/retirement-plans/mid-year-changes-to-safe-harbor-plans-or-safe-harbor-notices