TL;DR
'lgpPduPsLineEntryEpLNTenths' => '1196', ==================== value
Cur 1196, Low: null, Low Warn: null, Warn: null, High: null ========================= all set to null
"sensor_limit":137.54,"sensor_limit_low":101.66,"sensor_current":119.6 =========== why are these not null too?

#### output from discovery.php -v -d
<snip>
Data lgpPduPsLineTable:  
array (
  '1.1.1' => 
  array (
    'lgpPduPsLineEntryId' => '1',
    'lgpPduPsLineEntryLine' => '1',
    'lgpPduPsLineEntryEpLNTenths' => '1196', ==================== value
    'lgpPduPsLineEntryEpLN' => '119',
    'lgpPduPsLineEntryEc' => '204',
    'lgpPduPsLineEntryEcHundredths' => '2045',
    'lgpPduPsLineEntryEcThrshldUndrAlarm' => '0',
    'lgpPduPsLineEntryEcThrshldOvrWarn' => '75',
    'lgpPduPsLineEntryEcThrshldOvrAlarm' => '80',
    'lgpPduPsLineEntryEcAvailBeforeAlarm' => '35',
    'lgpPduPsLineEntryEcUsedBeforeAlarm' => '682',
    'lgpPduPsLineEntryEcAvailBeforeAlarmHundredths' => '355',
  ),
)  
Final sensor value: 1196  
Cur 1196, Low: null, Low Warn: null, Warn: null, High: null ========================= all set to null
Discover sensor: .1.3.6.1.4.1.476.1.42.3.8.30.40.1.19.1.1.1, lgpPduPsLineEntryEpLNTenths.1.1.1, liebert, AC RMS 1, snmp, 10, 1, , 119.6  
SQL[SELECT COUNT(sensor_id) FROM `sensors` WHERE `poller_type`= ? AND `sensor_class` = ? AND `device_id` = ? AND sensor_type = ? AND `sensor_index` = ? ["snmp","voltage",675,"liebert","lgpPduPsLineEntryEpLNTenths.1.1.1"] 1.06ms] 
  
SQL[INSERT IGNORE INTO `sensors` (`poller_type`,`sensor_class`,`device_id`,`sensor_oid`,`sensor_index`,`sensor_type`,`sensor_descr`,`sensor_divisor`,`sensor_multiplier`,`sensor_limit`,`sensor_limit_low`,`sensor_current`,`group`)  VALUES (:poller_type,:sensor_class,:device_id,:sensor_oid,:sensor_index,:sensor_type,:sensor_descr,:sensor_divisor,:sensor_multiplier,:sensor_limit,:sensor_limit_low,:sensor_current,:group) {"poller_type":"snmp","sensor_class":"voltage","device_id":675,"sensor_oid":".1.3.6.1.4.1.476.1.42.3.8.30.40.1.19.1.1.1","sensor_index":"lgpPduPsLineEntryEpLNTenths.1.1.1","sensor_type":"liebert","sensor_descr":"AC RMS 1","sensor_divisor":10,"sensor_multiplier":1,"sensor_limit":137.54,"sensor_limit_low":101.66,"sensor_current":119.6,"group":""} 30.84ms]

===================== "sensor_limit":137.54,"sensor_limit_low":101.66,"sensor_current":119.6 =========== why are these not null too?