The issue happened on SOL with IPMITool 1.8.9. Sometimes, BMC couldn't response in time, then IPMITool will re-send the key I pressed, which will make overlapped keys on screen. I checked the IPMI_LAN_TIMEOUT value in lanplus.h, it's 1.
But 1.8.8 uses 2, with that value, SOL works well.
I don't know why IPMI_LAN_TIMEOUT value is decreased from 1.8.8 to 1.8.9. Anyway, I had changed it back on my platform.
raphaeldeng@hotmail.com
IPMI_LAN_TIMEOUT is now, 1.8.12, back to 2, so I'm closing this one as fixed.