Posted: 22/07/2017 at 16:36
Do you ever see birds pecking at the lawn, particularly corvids like rooks? If so, they could be making the holes while they are after chafer or leatherjacket grubs which may be eating the roots and causing the dead patches. You can get nemasys nematode products which you water on to kill the grubs.
If not birds then a photo of the holes might help.