Hello XMC_Cross.
Can you please upload your server config files? As we cannot produce this on our end.

Here is my files for my events

Hello again.
We have tested this but we found no issues on our end even with your cfg files.
Do you have repro rate for this ? and does this occur with just specific events? Because it would be good to know if this occurs for example just in 2 out of 100 events.

It happens about 10 out of 100 for one of the c130 crashes which is at NWAF East of the Runway, about 1 out of 5 times the military train crashes that some people on my server been saying it is happening to more commonly. I also tried turning off the event and restart the server and turn the event back on and restart the server. This tends to be a temporary solution as two or three days later it'll start happening again.

First Screenshot is Novaya Train Crash which I encountered before a couple times, infected tends to range in different numbers.

Do the infected persist there indefinetely or do they despawn at some point?

They despawn after going away for a period of time. If it is the radius, what is the recommended radius for the infected despawn?

<event name="StaticTrain">
    <nominal>3</nominal>
    <min>1</min>
    <max>0</max>
    <lifetime>5400</lifetime>
    <restock>0</restock>
    <saferadius>500</saferadius>
    <distanceradius>1000</distanceradius>
    <cleanupradius>1000</cleanupradius>
    <secondary>InfectedIndustrial</secondary>
    <flags deletable="1" init_random="0" remove_damaged="0"/>
    <position>fixed</position>
    <limit>child</limit>
    <active>1</active>
    <children/>
</event>

cleanupradius>1000</cleanupradius>
Cannot de-spawn if player in this radius

This is an example we are using on vanilla. You could try setting cleanupradius to smaller value to see if that makes any difference.

Ill set it to 500, and let you know if it works better

Forgot to mention, setting it to a lower value works much better and barely ran into any leftover infected.