I don't have a fix, but you're not alone with this issue. I don't have the repopulation issue, but it definitely hangs for a few seconds at the end of a sentence when I use the voice input.
I just tried clearing the data for the Google Search app, got it set back up, but no dice. I'll try clearing the cache in recovery.
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Tried clearing the data in the Google Keyboard app, as well. That didn't help, so tried clearing the cache in recovery. That may have helped it by mere milliseconds, but it still hangs at the last word; especially with punctuation.
Your "THANKS" are not necessary, but I would appreciate them when due.