Rendering artefacts when drawing two close rectangle entities

Hi!

When I add two rectangle entities that are close to each other, I see following render issue from certain camera angles:


It seems that there is an invisible wall.

On the other hand, when there is no distance between the rectangles it works:


Or am I missing something when creating the rectangles?

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Sandcastle example: [See here](https://sandcastle.cesium.com/#c=tZLBb4IwGMX/lS+cIGMFptkSh2aL7rZkiTPbhUstn9istKYtGl3831dAjFOv3niv7/HrIzAljYU1xw1qGILEDYzR8KokX43nZx5r9FhJS7lEnXkh/GYSwKLWzhl0hVmryUKr8ltpkR8MP8jkPnjOZCZZQ+PSoHWwmMRx4vyWTlBabjkaQvPcbwgamaWyEDhoiQBMKZ1zSS2aI3fapRryBAuNaPw2D5Ak5CHsRP/pRLiTHty3tzlN9Nrn4OCVDqY5FUfeWAmlyfRtQjbcLl/Fakn9mDwGdXwfHrbeelMP7i5v/m9b/1abdkqVM+WfLawDXuilxm4Fjjr0Cy9XSluotPAJiSyWK1EPjeYV+0FLmGmKdTSNTqtpztfA8+GV3w+YoMa4k0UlxCffYeaN0sjlL6pCUfdhi481akG3dWyZjN5bkxCSRk5eb1qlxJzqszf/AQ)

Browser: Google Chrome Version 116.0.5845.187 (Official Build) (arm64)

(but happens in Safari too)

Operating System: macOS 13.6 (22G120)

Reproduce the issue using the linked Sandcastle example, with two nearby rectangle entities, and inspect the rendering behavior from the reported camera angles. Compare it with the zero-distance case and verify any change by confirming that the apparent invisible wall and related rendering artefacts no longer appear in both Chrome and Safari.

Written by the indexing model from the issue text.