Update on my new to me used Pro of unknown age. I've used it on fairly flat gravel trails including Palouse to Cascades rail to trail in Washington but haven't gotten around to trying it on steep hills until this AM. Rode it up and down my neighborhood road which gains 400ft in 1 mile with a couple 20+% segments. Only had 1 light on my battery at start and finish. I was in 1st-3rd gear (22t front, 40t rear, 700c bike) on the steepest areas and put in a good amount of effort. The motor didn't cut out even when going slow uphill and no slipping on the tire - I use 1" wide sanding belt for the friction layer. When I had tried this with my Mute version on same bike a year or more ago I turned back because the Mute didn't provide enough assist for me to make it. I'm not in great shape and have a bad knee that last year an orthopod told me was crying for replacement, so there's that. Overall I'm pretty impressed for what it is.
Unfortunately same day 15 miles into 25 mile ride the Pro broke down and is non-functional. From now on I'll just stick to my Yamaha mid drive gravel bike despite its 40+lb weight - no problems in thousands of miles on that plus TSDZ2 equiped bikes. It was a hilly ride but they all are in my area.