Hate this glitch, i tried to finish the last stage for at least 9 times, and get the badge because of that annoying glitch, changed my rating form 5/5 to 1/5. I won't change it back until they fix it.
You can do the first 17 level with only using human without repeating any level.
Just defend ur base with arrow...(from lvl 15 summon some dwarf to push the hobbits back)
use mana boost until u got 9999 then upgrade everything and spam knights + wizards
thats all
And always prepare for a counter attack because after you damaged the enemy's castle more than 50% there will be reinforcement coming for him.
If you succeed in pushing them back you will win the game for sure.
From lvl 16 u should buy some Dwarf to protect ur castle aginst the fast Hobbits but still dont buy too much just enough to push them back.Don't forget to upgrade your Tower
try to defend your castle only with arows and always use Mana Boost DO NOT waste mana on summoning upgrade your tower asap. When u got around 5000 Mana spam knights, wizard/archers(early game) and hobbits(to defend your other units)