What’s the Ex’s more impressive feat: being a functioning punk band for more than 30 years or never making a bad record. The Dutch group’s 25th album, their first since the departure of frontman-cofounder GW Sok and the addition of singer-guitarist Arnold DeBoer, threatens to break that streak. DeBoer’s political poesy lacks his predecessor’s acerbic wit, and his singsong delivery is much less bracing than Sok’s full-throated rant. Essentially, DeBoer is the Sammy Hagar of anarcho-punk. But when he lets his guitar take over, the band becomes a polyrhythmic dervish — lurching andlocking into angular post-punk grooves that pivot around bursts of noise and melodic traces of African pop.