MySQL server has gone away error shown when submitting form with big attachments

I have similar problem.

When I want to send a few  big files ( 40mb together) receiving this error

if the files are smaller everythng is ok.

Can you please tell us if you are still receiving the same error?

Also if you do, can you tell us what is the form where this happens for you so that we can check it out and see what is causing this.

Yes, still the same error.

problem arises when transferring files jpg. I suspect that the error arises when generating thumbnails for pdf file.

disabling generation of thumbnails to a pdf file solved the problem

We are very glad to hear that the issue has been resolved for you.

Let us know if you need further assistance.