A weekly project update by AWJ Marine showed progress at the site off the north Wales coast had been at a standstill, with 119 out of 161 array cables installed, since the end of June.
A spokesperson for project developer RWE Innogy said the cable-laying vessel Polar Prince, owned by UK marine experts Reef Subsea, was undergoing its five-yearly DNV class inspection.
"As it is planned maintenance, we wouldn't anticipate this preventing us from completing the project this winter," the spokesman said.
The vessel is due to return to the field next week to resume operations.
Gwynt y Môr's 160 Siemens 3.6MW turbines were finished being installed at the beginning of July.
When it is completed, it will become the world's second largest operational offshore development behind the 630MW London Array.
Gwynt y Môr is owned by German developer RWE Innogy (60%), energy supplier Stadtwerke München (30%) and technology giant Siemens (10%).