Your TTN Console screenshot cannot be the result of the decoder you’ve shown earlier. It shows string values, enclosed in quotes like field1: "1720.32", rather than true numbers like field1: 1720.32:
If meanwhile you added toFixed then ensure to convert to a number, like explained in my note about the unary plus-operator in my earlier link.
Given the new (different) values in the payload for step == 06 it seems the meter is sending updated values just fine. (And of course, if the values would be the same all the time, then you’d see a flat line, not a single dot.) And it seems the TTN Console decoder is working fine too—except for it currently returning string values, but apparently that works for the other fields just fine?
So, I’d guess the problem is in the configuration on ThingSpeak. What happened around the time 09:56:53 as shown in the screenshot? Maybe simply remove those 3 charts and recreate them? Maybe there’s some rate-limiting at ThingSpeak, meaning that you’re sending values too often?