SO-101 follower arm doesn't move during teleop (Windows) #77

Bug

Follower arm connects and has torque enabled (stiff) but does not physically move during teleoperation. Leader positions update in the display but follower stays locked in place.

Environment

• solo-cli 0.6.1
• Windows 11 Pro 10.0.26200
• Python 3.12
• Two SO-101 arms (STS3215 servos)
• Leader: COM11, Follower: COM13

Steps to reproduce

1. solo robo --calibrate all — both arms calibrate successfully with valid ranges
2. solo robo --teleop — leader connects, follower connects, camera connects
3. Move leader arm — positions update in terminal display
4. Follower arm does not move (but is stiff, torque is on)

Investigation

The follower's Goal_Position register (42) appears to be written, but the servo's Running Speed register (46) is never set. With speed=0, STS3215 servos accept the goal position but won't physically move to it. The so_follower.py only calls sync_write("Goal_Position", ...) without also setting Goal_Velocity.

Additional context

• Confirmed via direct scservo_sdk that torque enable register reads 1 on all follower motors
• Confirmed goal position register updates when written to (read-back shows new value)
• The same hardware works for reading positions (leader reads change when moved)
• Rerun viewer also crashes with gRPC transport errors on Windows
• Also encountered: servo multi-turn position accumulation (pos=34578 on wrist_roll) requiring DefineMiddle reset (write 128 to register 40)
• Also encountered: calibration crashes on negative position values when servos wrap past encoder zero point