Chipboard is not always squeaky clean
Often the problem with a chipboard can be the subfloor. Although chipboard is a recognised sub-base it has the least strength when nailed. It’s also possible that the back of the chipboard will blow when nailed.
Once the flooring starts to move, the nails can easily pull out of position, creating a loose floor and uneven gapping throughout. Manufacturers do not recommend nailing solid floors to a chipboard base.
You can correct any sub-base issues of using chipboard as the sub-floor by uplifting the flooring first, hopefully without any damage incurred, to be used again.
You now have two choices. You can uplift the chipboard and install a new 18mm plywood sub-floor. Ensure this is screwed done properly and there are no movements in the joists.
Alternatively, you could overlay the chipboard with a 12mm ply, assuming the damage done is quite minor. This should be securely fixed before the flooring is re-installed.
Where possible, an entirely new sub-floor should be installed.