The key issue here is why "wherever I":

I want to be clear about my test input. My test input was 5 lines. Each line contained the word 'wherever' (emphasis added):

1. I lay eggs wherever I happen to be, said the hen, ruffling her feathers and then shaking them into place.

2. and Trot fed it a handful of fresh blue clover and smoothed and petted it until the lamb was eager to follow her wherever she might go.

3. The habits of mind that characterize a person strongly disposed toward critical thinking include a desire to follow reason and evidence wherever they may lead,

4. But wherever they fought - in North Africa or the South Pacific or Western Europe -- the infantry bore the brunt of the fighting on the ground -- and seven out of ten suffered casualties.

5. scurrying for major stories whenever and wherever they could be found.

And that the unexpected transformations were consistent for the entire run. So if the command espeak-ng -ven-us --ipa=3 -q -f sample --sep=_ transformed 'wherever' as wɛɹˈɛvɚ sᵻɹˈɪlɪklˌɛɾɚfˈoː_ɹbˈiːˈɛf it did so for every occurrence of the word 'wherever' on each line of the sample input.