Sometimes the registration never gets to complete

Recently, we've had a few times where the individual registration button
produces this ?task=register.process_individual_registration like so:

events.prmi.org/?task=register.process_individual_registration

This in ie11 returns a 404, or displays nothing and in chrome goes to nothing but menus and footers.

Most times, the "Process Registration Button" goes straight ot complete:
events.prmi.org/dp-5-spiritual-warfare-b...ividual-registration
events.prmi.org/registration-complete?pt=1553646326


I'm trying to explain to someone what this does.
In about 10 of the 14 times it appears on our website logs, it appears before going to paypal. the other 4 times in our log it seems to abort.

I'm needing to explain to a user (who got a 404 from IE11) what this ?task=register.process_individual_registration is.

Can you explain to me?

Honestly, I have no clue why it happens. Maybe you can try to re-procedure the issue yourself and if you have a way to allow us to see the error myself, I will check it

Regards,

Tuan

Thanks for looking.. . .