Ikea fyrtur vs kadrilj electronics

Summary
Fyrtur and Kadrilj are generally compatible and you could exchange blinds material or even parts. If you got one - it can be easily upgraded to the more expensive one.

Price paid
I got some kadrilj which were sold by Ikea second hand (returned items) that someone returned in a bulk. It costed 350 PLN each, width 140cm.
My wife recently bought fyrtur (again from returned items) and paid around 200 PLN, same width.

During summer it is too bright so I wanted to use thicker material but I found some (false) information on the internet that those models cannot be simply swapped.
It might be that there are incompatible versions as IKEA often upgrades their products and design without sharing this to the customers (because devices are not meant to be disassembled).

This time my wife bought a device that is faulty. I am not yet sure whether it is a faulty motor or electronics or something else but it is simply broken. The rule in general with IKEA is that you should not return 2nd hand goods (but it probably depends on many factors).
I started with internet search for the device teardowns and did not found many information. Some of them presented how to disassemble major parts.
Then I compared mechanisms of both devices. To my surprise the motor was exactly the same. So was the shape and size.

Next steps for me:
- exchange motors with the electronics and check if this is motor or electronics which is faulty
- disassemble faulty element (which would be challenging for sure) and find why it is faulty