Hesitation in pronunciation

[hal_32726]

Using Callie 6.1.5 on a Raspberry Pi with swift 6.1.5:
'dad' pronounces correctly when spoken alone. However in the phrase "Today is dads birthday" there is a "catch" when pronouncing dad--it sounds like "today is dehads birthday" with the emphasis on the "ads" syllable.
I tried inserting a phonetic phrase for dad, but the problem persisted.

I have noticed this with other statements also, but I haven't logged the issue. I have it saying the time and date, and sometimes the day name is pronounced correctly, other times it has problems similar to the above example.

Any suggestions for a solution or work around?