Found a bug in ZED SDK 5.5: GEN_3 tracking keeps adding keyframes even when the robot just stands still. 265 of them in 9 minutes, CPU from 31% to 135%, the map file swelled to 70-80 MB. Workaround: by default the camera only localizes in the existing map and extends it only for a new map or during exploration. At rest the camera process is now 17-45% CPU instead of 134-185%.