Calibration Procedure (Nicalay2's note : it is only needed to do it on the main tracker):
1- Restart the trackers.
2- Once connected, hold the trackers at chest height, lens facing forward, and hold them still for 10 seconds [making sure they are tracking].
3- Slowly move the device horizontally in a figure-eight pattern for 1 minute in an area with rich visual features.
4- If using a dongle, unplug it [or you can also close Vive Hub]. If using Wi-Fi, shut down the tracker server. Allow the trackers to enter sleep mode and rest for 2 minutes to allow the extrinsics to be recalculated.
5- Restart the trackers to apply the updated extrinsics.

Nicalay2's PS : after restarting the trackers (step 5), make a new room map