So, do we all agree on the fact that my coin has a problem?
And that tails should occur much more often?
And that a 77% heads ratio is NOT normal? That is should be much closer to 50%?
No, for what I can see it's everything ok.
because you have taken a small interval for your data (just 100 numbers), this is why you have seen a biased value.
Grossly, if you continue to bet, in a random and infinite progression, the number of tails and heads must be around the same (50% ...) .
For sure It cannot be exactly the same (since there is always a grade of randomness) and even if you see a big difference it's just related to random pickup of the values.