After testing 1.7.1 for the last two days watching at least two hours of shows on Discovery Plus, I have not received any stuttering or freezing. This is, indeed, promising.
Something else I noticed when updating the Discovery Plus app to 1.7.1, I noticed my Roku OS was updated to 10.0. I was pretty sure I was on a 9.x OS version the last time I looked. Is it possible there was a ROKU OS update, along with the Discovery Plus app update to 1.7.1, that fixed the freezing / stuttering problem?
At any rate, I will continue to test and report back with any new info.
As a side note, my support ticket with Discovery Plus Support, ticket 414489, is still open, and I've not received any further updates from Discovery Plus Support as of yet.