GTM namedb zone files missing

Recently our clients started complaining that they can't resolve certain domains for example advisor.markerscope.com gets resolved sometimes and sometimes they

 

get nxdomain error. So I logged a call with f5 and they say zone files are missing for that domain. We are also missing zone files for other domains .How can this happen? I thought when u create a wideip it will create a zone file.

 

 

Is there a setting in gtm that can turn off creation of zone files ? Because I have a spare gtm and I created a dummy domain and it did not create zone file.

 

Thanks in advance for help

 

 

Kirit