Hi Joel,
Thank you for bringing this to my attention!
Are you able to upload an example .oml here (or message an example directly if confidentiality is required)?
I'm having trouble re-producing this behaviour. I am able to search a list of 10,000 items without problems.
You can view my temporary test at
https://cstacey.outsystemscloud.com/MultiSelect_ReactAndMob_React_Demo/MultiSelect_ReactAndMob_React_Demo_10000items
check the 10,000 items radio button and wait about 3 seconds for the list to generate


We will get to the bottom of this, I'm just struggling to re-produce the issue at the moment.
Kind Regards,
Chris