I am experiencing this exact same issue. I have a Paranormal 167 / DNA 250 and it was working perfectly, but now will only charge between .54 and .59 amps. I have also noticed some battery shenanigans like yours, where my mod tells me my (brand new) 18650 batteries are ~70% full, but my external charger reads them at 4.2v, I have also vaped until my batteries are down to 30-40%, then charged them internally (at around .59 amps) for a while until they read around 70%... and then I vape for a minute or two and the battery indicator will jump up to almost 100%.
Using eScribe, I have also noticed some behavior that seems linked to the low amperage issue. I have seen people suggest that the mod compensates for voltage sag by lowering the amperage... but those people were also suggesting that the voltage sag was coming from the charging cable, which is NOT the case for me. When monitoring 'USB Voltage' in eScribe while connected to my PC, I can see the voltage rise and fall between 5.0v and 4.27v every few seconds, with matching dips in the amperage... but it still never rises above .59 amps.
I'm confused and unhappy, because the reliable internal charger was a big reason why I bought this mod. The chip also forgets your coil when you remove the batteries to externally charge them, which can cause loads of TC problems... and TC is the other big reason I bought the mod.
I apologize for not attaching eScribe screenshots, but this issue has been posted about before (with no solutions?) and all of my information would just look identical to theirs.