Fifteen month old puppy.  Trailer is a lot less squirrely handling though.

I just built a rear wheel with a Bafang 100W hub.  Bonus is the power cable exits on the disc side instead of exiting the center of the right side of the axle.  It also came with 19mm capped axle nuts.  What a difference from stock.  24.5mph instead of 20mph.  I am waiting for the back ordered Bolton controller to arrive.  I expect 28mph after I install it.

I just installed a Bafang 1000W rear hub.  What a difference.  There are photos of the stock RAD motor armature next to a Bafang 750W armature that shows how much smaller the RAD armature is compared to a Bafang 750W armature. 

These are cable actuated hydraulic brakes that allow you to use the stock brake levers:  https://www.alamedabicycle.com/product/trp-hy-rd-394672-1.htm?variations=3854379,3854380,3854382?utm_source=google%20shopping&utm_medium=organic&gclid=CjwKCAjwu5yYBhAjEiwAKXk_eAWDVqc_X_UTuUqYDdi39ml3Z5Y1ynR5LKc0z7GP_LX7NdnXDV5GBhoCe0AQAvD_BwE

Too bad they could not maintain their mobile service.  No wonder with the price of gas, and everything else involved in mobile service.  With their electronics warranty issues they should have mobile service though.  Perhaps the could use Velofix as a sub contractor for mobile warranty service.  The second wave of layoffs are throughout industry.  Even huge companies like Tesla are doing it.

I just took a test ride using a trailer, and my 75 pound dog.  Trailer is outfitted with 100 psi 700c tires.    Mandatory use of  the pedal assist on any hill.  Throttle seems to provide slightly less power than the pedal assist on hills.  Must be due to my added human sourced energy input.  Speed ranges between 7, an 14 mph uphill.  Better to forget the affordable price, and get a category 3 e bike for towing a large dog in a trailer.  I have to wait for a Bolton controller to increase the motor torque which should help.  Meantime I will use my cat 3 e bike for towing.  Much faster uphill.

Try replacing the brake cable.  It may be defective causing spongy lever feel.