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If they have fused you will just need to spend time trying to wiggle them or use a craft knife gently as per the images provided. This is exactly why I posted a 'loose' version... another thing that may help, but you need to be careful with this, is to work out the areas that are sticking and pour near boiling water onto that area then quickly try to wiggle / rotate it. The heat will soften the plastic a fraction and that can help it break free.
If all else fails scale it up by 5 - 10% and reprint it. That will increase the internal clearances to make it easier to free up.
I hope this helps...