The current release is 2018.2 but still this issue exist.
I have the same problem now.
The only difference is I am setting field values.
The setting of field values are ok with line 0 but when it comes to 1,ย
<span style=”color: #000000; font-family: ‘Open Sans’, Helvetica, sans-serif; font-size: 10.6667px;”>{“type”:”error.SuiteScriptError”,”name”:”SSS_INVALID_SUBLIST_OPERATION”,”message”:”You have attempted an invalid sublist or line item operation. You are either trying to access a field on a non-existent line or you are trying to add or remove lines from a static sublist.”,</span>
For now I will try setting the field values on the client script instead of in the suitelet.