I’m glad you managed to find a culprit.
Caching plugins aren’t very useful for MainWP Dashboard since very little of important content is static, so we’d recommend disabling that plugin.
Our general recommendation is to MainWP Dashboard on an otherwise empty site and not on a production site.
In the last version of Domain Monitor we’ve decided to show N/A for unsupported TLDs instead of January 1st 1970.
Please check out our KB for a list of supported TLDs: