TTS voices have evolved a lot in recent years but very often they get the accents wrong in several words.
If you have the patience, the only way to limit this problem is to install Vocalizer Full 3.7.2 on your device, download voice Xander, (or Claire) and in iGO you use the Universal Unisex voice, if it's dictionary.voice is out of date replace it with one of the voices you are currently using.
With this version you can create your own User Dictionary inside the program where you can customize the words that will then be used instead of the "bad" ones.
Spoiler: APK
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