Looks like NTP servers with DNS names are retained, these with pure IPv4 Addresses are not. Please create a support ticket via httpd://my.netgear.com/ or call them on the local Netgear Support number.

Digging into this a little more with version 1.1.1.8, I factory reset one of the two switches that I used for testing. After factory reset, the SNTP servers are autopopulated by Netgear. I then changed these SNTP server to some of my own choosing. After reboot, they are again gone and deleted. But even worse, using a backed up settings file to restore the previous switch settings did NOT restore the SNTP servers. This is getting very strange Netgear.

I was just able to reproduce the same bug with 1.1.1.8

I don't know what type of Q/A Netgear is running but a SNTP bug that is persistent even with the latest version and can be early reproduced on several switches of the same model should get the company's attention

Here are my screenshots from before and after:

1.1.0.9. works with SNTP settings:

then upgrading to 1.1.1.7:

As you can see SNTP entries are empty and gone.

Switching back to 1.1.0.9

SNTP entries are still gone and have to be reset.

Haven't touched the SNTP config for years since the  MS510TXUP is in service here. Just changed the DST to show the correct zone. 

Uptime is almost 27 days now (since building power works).

Please tell us a little bit more about your SNTP -and- the Time configuration.

Regards,

-Kurt.