There are a few reasons why this could be happening but here is what it looks like.
A grouped-view rendering issue is occurring. This is what happens when there are multiple nested group levels along with summary/rollup fields. Airtable can sometimes miscalculate the height of the row and clip the last ones.
Don’t worry your data is still there; if you collapse/re-expand the group and remove one grouping level or recreate the view it is usually fixed. Also if you reduce visible fields or switch row height to “Short” this can help.
Grouped views are more fragile than standard grid views and if this is consistently reproducible, it should be reported.