I'm definitely seeing similar (mis)behavior when attempting to cast spells, with the spell book appearing to be stuck at the second page or so. You can indeed get around this by clicking page down and up, it seems clicking on show all spells works as well.
In a recent game I followed up Pillar of Flame with Tremor and then the enemy stack will be wiped out, as it's supposed to.
Typically it's impossible to have troops stationed near all Outposts or Cities for that matter. Hence when enemies or monsters cross the border, it's sometimes necessary to (ab)use Pillar of Flame and reduce those stacks to ashes. At least that's the theory. However in 0.915 some of the units from these stacks manage to live on despite being reduced to zero hit points. These miraculously surviving units then obviously see no problem trashing my Outposts, shrines and so