This seems to happen to a small group of people and is something either engine related or system related, not something we can fix. Someone recently reported that updating their graphics drivers fixed the issue so you might try that.
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If you found the issue, it'd be helpful to hear what solved it for you. It's an issue that gets reported from time to time but is never something that seems to be a 'Sileo' issue as much as it is something external to that. If it's a Ren'Py thing, hopefully an engine update will drop soon that'll rectify the issue. Being what it is though, it's not feasibly something our code is causing.