Sim800L - Avoiding 604 Error or the cause ?

Hello,

I am using sim800l module successfully without a problem to send location data every 15 seconds. My problem is every few hours, for 2-3 minutes my logs show an 604 http response which means STACK BUSY, on the internet I have made many search before opening this topic but no clear cause or solution is provided. Does anyone has an idea what causes this error or how to avoid it?

Thanks