It looks likely that during all this, Interleaving has been turned on. Thus bringing you down from 8128kbps sync to 7616kbps.
You may like to look into that.
Having re-synced later in the afternoon it has improved:
Uptime: 0 days, 1:20:19
DSL Type: G.992.5 annex A
Maximum Bandwidth (Up/Down) [kbps/kbps]: 1,261 / 8,765
Bandwidth (Up/Down) [kbps/kbps]: 1,256 / 8,187
Data Transferred (Sent/Received) [kB/kB]: 0.00 / 0.00
Output Power (Up/Down) [dBm]: 12.0 / 18.5
Line Attenuation (Up/Down) [dB]: 22.5 / 40.0
SN Margin (Up/Down) [dB]: 6.5 / 6.0
Vendor ID (Local/Remote): TMMB / BDCM
Loss of Framing (Local/Remote): 0 / 0
Loss of Signal (Local/Remote): 1 / 0
Loss of Power (Local/Remote): 0 / 0
Loss of Link (Remote): 0
Error Seconds (Local/Remote): 5 / 0
FEC Errors (Up/Down): 17 / 47,269
CRC Errors (Up/Down): 17 / 214
HEC Errors (Up/Down): 214,895 / 204