This is probably more a server issue with Plesk etc but relates to Processwire.
I have a very long web form which takes the average user 3-5 minutes to complete. I know it's crazy but it's a client-driven thing.
Occasionally, my client has been emailed by users that when they eventually his Submit, they get a general 500 server error.
I did some research and looked at some logs and it seems to be some type of time-out issue. I guess that makes sense if the form takes minutes to complete as the first two fields of the web form are attachment uploads. I'm thinking that attaching files establishes some type of session but that session expires by the time the web form is actually submitted.
Does that sound plausible enough?
I plan to suggest moving the attachment fields to the end of the email, disabling the webform CSFR too and seeing if things improve.
Does my theory about file uploads and session time outs sound plausible?