I am a little bit behind anon848905. My PT is 8.0.75.7.
In Scripture Reference Settings section Reference Format we have in Extra Material box “a|b|c” If I remove all of these, the Basic Check will flag out every reference where the letter a appears as “Invalid book” (which is a bit strange in itself). If I keep them all, only this John 18:38 case is flagged. Other cases where the letter b appears are never flaged out.
However, and after a little experimenting, if I only add the letter a to the Scripture Reference settings Extra Material, PT will happily accept all the references. But why is this? What is the logic behind the checking prosedure?
BTW, in language settings (Other Chars) all normal Latin charchers are listed in Verse segment characters section.