namecheap is also great IMHO
That doesn't make any sense. As long as you set up the proper records in your new DNS provider prior to switching nameservers, there'll be no interruption.
It sounds like you switched nameservers first, assuming the records would just transfer over?
So, when you point to new nameservers, anyone pointing to namecheap's dns during propagation will get SERVFAIL.
It sounds absurd... but I've gone back and forth with support about it, with no solution.