Yes, I had issues with my first left crankarm, was replaced under warranty without any hassle. The original crank pinch bolts were actually bent. I got the replacement, installed per the directions/specs. That stayed tight only a few rides, got loose again. I reset it yet again to specs.
Since that time, July of 2022, I have made no more adjustments and it has stayed tight. I’m confident the original left arm bolts were either defective or possibly the arm itself not even drilled correctly, causing the bent bolts and loosening crank.
But why it took about 3 times to get it to hold, when it was torqued to spec every time, I don’t know.
IMPORTANT TO NOTE, however, that the MAINTENANCE GUIDE for the KICKR BIKE says to CHECK CRANKARM BOLT TIGHTNESS EVERY 96 hours or 4x A YEAR.
I’m sure this need varies according to how big, strong, and violent you are on the bike.
I would check pinch bolts for straight-ness (roll them around on a flat surface and see if the roll true or wobbly) and then be sure to torque everything to spec:
(3.5Nm for center, preload/tensioning bolt, 15Nm for pinch bolts.)
Here’s a link to a long answer I wrote on another thread.