Money Disappearing from IFISAs

As I, incredibly, had a month where I didn't experience a default that wiped out my returns, I've now found that I think I have this issue i.e. despite apparently being paid interest, in doing my monthly checks my balance appears to have moved almost nowhere.

So in summary, usually I lose money each month to defaults  but even if I don't then I still lose money? I'm really really not feeling the love for Zopa at the minute.