This sort of thing is virtually always an issue with the synth, so it would be worth reporting to the synth maker with your example text, too.
That being said, two things:
1. I'd use the voice dictionary.
2. Make the matching string "as well as" then try something like "as well As" or "as well az" (or perhaps azz) for the replacement.
You might also try something as simple as "as" for the match and "As" for the replacement and see if that fixes it.
I had a similar experience with one voice saying "cup" as "Cuban Pesos" when it was used in recipes in an ingredient list. Just the simple replacement of lowercase "cup" with the capitalized "Cup" fixed the issue.
Brian - Windows 10 Pro, 64-Bit, Version 20H2, Build 19042
Always remember others may hate you but those who hate you don't win unless you hate them. And then you destroy yourself.
~ Richard M. Nixon