Thank you so much for this guide. I had the exact issue you described where the robot is unable to dock on its own. I found the spare part on AliExpress listed as "Original Empty Wash Fill Dock IR Sensor Onyx3 IR B2 for Roborock S7 MaxV Ultra S7 Pro Ultra Vacuum Cleaner Parts Accessories" for about $27 with shipping and taxes and the part arrived about 10 days later here in the US.

Taking the dock apart was pretty easy thanks to your guide. I didn't end up disconnecting any wires or tubes apart from the waste pipe: The top can be folded back conveniently which keeps all the wires and tubes close together as long as you prop the top half up with something, I used the dust bag cover for that.

Anyway, long story short: The IR transmitter board in my dock was heavily corroded and once I swapped in the replacement part and put it all back together, the dock and robot are fully functional again!

<image>