ESV Frustrations

I love the ESV and use it all the time...but sometimes it furstrates me. So, in Jeremiah 33:8 there is a distinction (in the Hebrew) between sin and sins. The ESV renders both as 'sin'. Then, in v 11 it uses the archaic 'mirth' even though the Hebrew is the same as in v9 where the ESV uses 'joy'.