sequence caches and synonyms

We noticed that if we ask a package to return the next value which would be used for a table entry (done using a sequence), we get a number.

If we go through a local synonym to ask the same package to answer the same question, we receive a slightly different answer.

Is it possible that there are two caches of sequences values, depending on how the package which refers to the sequence is executed? I suppose if two users are entering records concurrently in the same table, they each have their own set of cached sequence values (?).

We don't think this happened in 11g, it only seems to be happening in our 12.2 databases.

I will log an SR as well, just thought I might ask this list first.