Steps to reproduce:

1. Create LLD rule and use LLD macros:
2. JSON for this LLD rule contains backslash "\" in property, which used in LLD macro

   [
   {
   "ProtectionGroup": "cluster-006-VM",
   "DataSource": "VM\\server-815",
   "ExecutionState": 2,
   "ErrorCode": 0,
   "ErrorString": "",
   "LastJobStarted": 1564851600,
   "LastSuccesfulJob": 1564851600
   },
   {
   "ProtectionGroup": "cluter-006-VM",
   "DataSource": "VM\\server-816",
   "ExecutionState": 2,
   "ErrorCode": 0,
   "ErrorString": "",
   "LastJobStarted": 1564851600,
   "LastSuccesfulJob": 1564851600
   } 
   ]

1. Use LLD macro with backslash in Item Prototype: Full code:

   $.[?(@.ProtectionGroup=='{#PG.NAME}' && @.DataSource=='{#DS.NAME}')].first()

    

Result:

Error in LLD rule:

Cannot update item: invalid value for preprocessing step #1: unsupported construct in jsonpath starting with: "'VM\server-815')].first()".
Cannot update item: invalid value for preprocessing step #1: unsupported construct in jsonpath starting with: "'VM\server-816')].first()".