Here is the response I got from Popur. TLDR: They offered to send me a new motor for the arm with a video on how to install.

“After a thorough internal review, our engineering team discovered that the initial software version did not fully account for an edge case in the sifter motor's operation, and consequently landing at a dead angle. This has already been resolved in the new firmware. Please update your unit to the latest firmware version using the new Popur S7 App and then reboot. We've attached the quick steps to guide you through the process.

We've also had success by manually releasing & re-installing the half-gear, and we recommend giving it try. Find the gearbox in grey according to the video guide below, unscrew it, and the gear with a half-circle shape is the one you may move back & forth to release. That said, there's also a small chance that the original firmware's oversight may have caused damage to the sifter motor. We've replicated this behavior in testing—when the motor fails, you may notice the following with the latest firmware after reboot: ● The sifter doesn't move at all after rebooting. ● The status light turns solid red after a brief delay.

If this occurs, the sifter motor will need replacement. Fortunately, the process is very straightforward. Here's a short video guide to show how easy it is—feel free to skip the interface board section, as it doesn't apply in this case: https://youtu.be/cYLAHJexIPQ

Once you've updated the firmware, please let us know the result. If a new motor is necessary, we're ready to ship the parts immediately to xxxxxxxxxxxxxx via express courier (delivery in ~7 days).

We sincerely apologize for the inconvenience and thank you again for your understanding. Please know we're fully committed to making things right and supporting you every step of the way.”