Pathauto alias produces inconsistent aliases
Check settings in  Administration » Configuration » Search and metadata » URL aliases there is a Strings to Remove like this:


  a, an, as, at, before, but, by, for, from, is, in, into, like, of,
  off, on, onto, per, since, than, the, this, that, to, up, via, with


thats why your A is removed i think.