When Force Cone is activated against a character holding Reflect Missile, after a successful roll, it should slide the caster that used Force Cone backwards two squares (unless they are against a wall). However it didn't work on my elf wizard when he used it, the wizard only took the damage, didn't slide back the squares. The other force spells such as force bolt and force blast have the effect that when reflected, it sends your character backwards however many squares the spell is for. Has anyone else seen this bug?
Telekinesis and Gusts/Winds of War will allow the person to move, but force bolt/blast/cone do not. The reason is slide back moves back from the caster, but since the caster is the one having it reflected back on themself, nothing happens. One can not be moved back from oneself. If in your example it was a warrior that had the reflect missile, it's not the warrior that is casting Force Cone, the block is making the Wizard cast Force Cone on itself. Well if a character pushes itself back from itself, which way does it move? There's no valid answer because it's non-nonsensical.
Although I get the mechanic of it and won't call it a bug, the intuitive understanding would nevertheless be "I Slide Back'd myself from the target I hit who blocked, thus the effect would be the reverse of my moving the target -- I'd move the same number of spaces in the exact opposite direction." $:^ `