Repeating final year (for the first time) and received a lower maintenance loan?

I am repeating my final year of university this year.
I applied for student finance and last year my maintenance loan was £7,689 however I just opened my entitlement letter for this year and it says that my maintenance loan is £3,397 this year, why is this? I heard that if I have not previously used my gift year funding then my maintenance loan should be the same as last year? Have they made a mistake? I have not provided any evidence of my household income when applying because I thought they would assess me on last years income, could this be the issue?