Reg: Flash Symbol & Gerber output

Hi
I need your help to solve below issue

Current I am doing very old board revision activity , which used negative artwork for the plane & flash symbols for PTH.

1) I have not worked with negative plane artwork before , connection shown in is a very thin “+” sign on plane as shown in image , I really doubt
    how exactly its connected to [ plane fully or only + connection ] . This pin carries 15A current !, I suggested to change the plane to positive artwork , due some standards
    they didn't allowed me to change . Please let me how can I increase the connection width ? I exported libraries  & checked but some issue with flash symbol .
2) While generating Gerber files its throwing below error & unable to process

Your suggestions are highly appreciated

Best Regards,
Girish Kumar