Floating point error from UGameViewportClient::SplitscreenInfo causes this issue.
FMath::TruncToInt( 3240 /*ViewportSize*/ * 0.333f/*Ratio in SplitScreenInfo*/ ) = 1079
I suggested a following temporary fix to the licensee.
#if 1 // temporary fix takashi.suzuki@epicgames.com SplitscreenInfo[ESplitScreenType::ThreePlayer_Vertical].PlayerData.Add(FPerPlayerSplitscreenData(0.3334f, 1.0f, 0.0f, 0.0f)); SplitscreenInfo[ESplitScreenType::ThreePlayer_Vertical].PlayerData.Add(FPerPlayerSplitscreenData(0.3334f, 1.0f, 0.3334f, 0.0f)); SplitscreenInfo[ESplitScreenType::ThreePlayer_Vertical].PlayerData.Add(FPerPlayerSplitscreenData(0.3334f, 1.0f, 0.6668f, 0.0f)); SplitscreenInfo[ESplitScreenType::ThreePlayer_Horizontal].PlayerData.Add(FPerPlayerSplitscreenData(1.0f, 0.3334f, 0.0f, 0.0f)); SplitscreenInfo[ESplitScreenType::ThreePlayer_Horizontal].PlayerData.Add(FPerPlayerSplitscreenData(1.0f, 0.3334f, 0.0f, 0.3334f)); SplitscreenInfo[ESplitScreenType::ThreePlayer_Horizontal].PlayerData.Add(FPerPlayerSplitscreenData(1.0f, 0.3334f, 0.0f, 0.6668f)); #else SplitscreenInfo[ESplitScreenType::ThreePlayer_Vertical].PlayerData.Add(FPerPlayerSplitscreenData(0.333f, 1.0f, 0.0f, 0.0f)); SplitscreenInfo[ESplitScreenType::ThreePlayer_Vertical].PlayerData.Add(FPerPlayerSplitscreenData(0.333f, 1.0f, 0.333f, 0.0f)); SplitscreenInfo[ESplitScreenType::ThreePlayer_Vertical].PlayerData.Add(FPerPlayerSplitscreenData(0.333f, 1.0f, 0.666f, 0.0f)); SplitscreenInfo[ESplitScreenType::ThreePlayer_Horizontal].PlayerData.Add(FPerPlayerSplitscreenData(1.0f, 0.333f, 0.0f, 0.0f)); SplitscreenInfo[ESplitScreenType::ThreePlayer_Horizontal].PlayerData.Add(FPerPlayerSplitscreenData(1.0f, 0.333f, 0.0f, 0.333f)); SplitscreenInfo[ESplitScreenType::ThreePlayer_Horizontal].PlayerData.Add(FPerPlayerSplitscreenData(1.0f, 0.333f, 0.0f, 0.666f)); #endif
Result
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There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-85227 in the post.