I globally blocked some ranges (e.g. 151.19.0.0/16) which I need to whitelist in a single project (it.wiki). It seems to work only for the first time, as soon as I reblock these ranges I'm unable to whitelist them. "Disable this block" checkbox is already checked but the block is actually active. Because of this bug I currently have to choose between setting free a truly dangerous vandal and blocking a whole ISP.