From release 8.5.5, a software defect has been discovered that affects PTP820S 1+1 HSB configurations. This may result in the HSB radios failing to respond properly to protection switchover triggers:
1. Loss of active unit – does not switch.
2. Lockout – does not switch.
3. Radio/Ethernet interface failure – does not switch.
4. Manual switch – does not switch.
The permanent fix for this issue will be available in the next release.
The recommended workaround is to downgrade the affected system to Version 126.96.36.199.0.495.
PTP820S systems running Version 188.8.131.52.0.495 do not support Line Protection mode with LACP electrical GbE ports. Only Split Protection mode (connecting an optical GbE port of each unit to an optical splitter) is available with this software version.
Please refer to the forum post here, for more discussion on this issue.
The FSB (FSB9068) is attached here for reference.