It's definitely tough when you've got no visibility of what's going on, and when dates are inconsistent
Relax, I'll think you'd find that other priorities come into play e.g. Recruitment staff attending Assessment Centres which means that other tasks get delayed. There can be sick leave and/or holidays (extra staff wouldn't be seconded to cover), plus some Recruitment staff are part-time. It might be slower than you'd like and it won't change the outcome, you are either suitable or not, be patient, as frustrating as this is.