Hello,
I just want to come here and say that my issue has been fixed, but it was through a different method I found that I feel like I should post here in case someone else has this issue.
I did try getting the most up to date versions of each component, but that didn't fix it, and neither was downgrading to a lower one fix it. I went ahead and started remaking the site with the same template just to only have hikashop and jevents/rsvp pro only to find out that once I got to checkout, I was getting the same issue with it crashing if I did anything inside checkout. I did no save the error message, but it was a completely different one that was related to the hikashop plugin itself. I noticed that I had my registration setup to allow user creation instead of just guest checkout, so I went back to change it, went through checkout again, and it was working.
This made me go back to my original site that was crashing and I went ahead and changed the checkout so I can save the changes. I disabled the ability to login during checkout, saved, then reenabled it and saved again, and for some reason, this fixed my issue.
I do not know why editing my checkout in configuration and saving it fixed the issue, and I do not know why the payment trigger plugin was causing it to crash the site, and with changing the checkout, made the plugin work again. I am not sure if it's the template I'm using or with some modules/components that came with its quickstart, but it's very strange to me that simply editing how the checkout page looks would fix this issue.