I can not see checking for "order[i]>63". But in this code I see "int num[64] = {0}". What result of using num[68] for example?

Too small size of mem in calloc(sizeof(char), strlen(text) * 2 + 1);
You did not count space after every number. In "hard" strings like "zzzzzzzzzzzzzz" you may crush programm
And tecnical mistake: void *calloc(size_t nitems, size_t size) - Arguments are reversed

yes, logical error
in this code very hard to find it