Tried changing my rear springs tonight on my sapph but I couldn't get the old ones out

I've changed the rear springs on 2 xr4x4s and an escort cossie before but for some reason I couldn't get them out tonight, I even went to remove the 2 17mm bolts that hold the rear beam to the chassis and one of the captive nuts gave way

<-real.
Any tips for changing them would be appreciated