I have not had this issue myself, however there is a guide & video tutorial on getting sourcenext version installed and ready to go by checking out the 'Guides' section.
https://www.speedrun.com/re2/resources
It could also be the quality of that iso you may have.
On the left side bar there is a link to the RE Community Discord server that could provide more inside info to the issue you are having with installing if the problem continues.
Most of the time, taking the hit during Leon A is the most consistent way of getting through that gate.
As the others mentioned, during the WR attempt is when you are looking for the RNG of a green/brown shirt zombie to be hitting the gate. A quick shot aiming down almost guarantees a stun on the front zombie, pushing the second behind it into a stun as well. The third zombie in the court itself should be far back enough where you can run by and make a sharp left when you enter the gate not to be hit.
Hey, everyone!
My name is Th3BetaCat, Beta for short. After watching a handful of speedruns, casual runs and modded plays I've finally decided to give my first try at speedrunning.
The game I will be trying first is RE2. Thanks to the wonderful people on the RE community, I was able to set up Bio2 as well as a few of the tools. I have yet to setup the autosplitter. I've seen a few livesplit tutorials as well as the tutorial linked in on of the threads here to set up the autosplitter.
I'm still not sure how it will go, I never though I'd take a shot at speedrunning anything but the more I watch speedruns on RE2 the more I wanted to try it. So, here I am!
I look forward to being a part of this community!