Is it a network problem - either on your LAN or between your router and emoncms.org? (i.e, your ISP?) I don’t know how “quality” is arrived at; if it’s documented anywhere, I’ve no idea where to look. If it’s purely the number of received packets versus the expected number over the same period, then a transmission problem - or even a variable delay which causes packets to fall into the wrong ‘slot’ - would explain it.
[What I mean by that is, if you’re using PHPFINA at 10 s rate, the data is simply dropped into the “now” time slot as it arrives. So let’s say a packet arrives 9.9 s into the time slot consistently, all is well. but if one packet gets delayed by 150 ms, it misses its slot and goes into the next one. If the next packet isn’t delayed, it goes into its proper slot and overwrites the late one.]
Why ct4 should be different, I’ve no idea. I don’t know what goes on inside the ESP8266, nor how the data is sent over the Internet (i.e. how many packets, of what size). But there’s no law saying that the data needs to be sent in that order, so you could shuffle ct4 up into 2nd or 3rd place, if you wished.
You don’t need to send empty values for anything you’re not using, so you could comment out ct3, maybe vrms, and pulse.