Fro the log file it get following incorrect return :-
Run remote command [/opt/vc/bin/vcgencmd measure_volts core|cut -c6-11] Result [6] [initia]...

However, running the command directly /opt/vc/bin/vcgencmd measure_volts sdram_p|cut -c6-11 gives the correct result i.e. 1.2250

also, get the correct value via zabbix_agentd
i.e sudo zabbix_agentd -t system.VoltageCore
system.VoltageCore [t|1.3125]

This is working fine on two other raspberry pis with exactly the sae configuration and software versions