reportlab - 502-backend

I try to print pdf and then get this error. I use method get to link /Print_Expense?Eid=E00002&id_project=PJ00001. i just click button and then it return error in spite of this rote not ganerate pdf but sometime it generate and sometime it didn't anything and turn 502-backend

I just use reportlab and svglib to generate pdf how can i solve this problem? please.

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Error code: 502-backend

Have you checked your web app logs yet (esp. the error log and/or the server log)? The 5XX errors mean (basically) that your web app is crashing for some reason.