I have a website that uses CesiumJS version 1.63.1 (yeah, old) to display locations on the Earth. I haven’t modified the site for years (2020?). Recently, it started displaying errors when the page is rendered.

When using the minimized version of Cesium.js, the following is displayed in the browser:

An error occurred while rendering. Rendering has stopped.
RangeError: Invalid array length
RangeError: Invalid array length
    at updateFrustums (https://mywebsite.com/addins/cesium/Build/Cesium/Cesium.js:23:2828996)
    at View.createPotentiallyVisibleSet (https://mywebsite.com/addins/cesium/Build/Cesium/Cesium.js:23:2832470)
    at executeCommandsInViewport (https://mywebsite.com/addins/cesium/Build/Cesium/Cesium.js:23:3013516)
    at Scene.updateAndExecuteCommands (https://mywebsite.com/addins/cesium/Build/Cesium/Cesium.js:23:3010501)
    at render (https://mywebsite.com/addins/cesium/Build/Cesium/Cesium.js:23:3022237)
    at tryAndCatchError (https://mywebsite.com/addins/cesium/Build/Cesium/Cesium.js:23:3022474)
    at Scene.render (https://mywebsite.com/addins/cesium/Build/Cesium/Cesium.js:23:3024337)
    at CesiumWidget.render (https://mywebsite.com/addins/cesium/Build/Cesium/Cesium.js:23:3267378)
    at e (https://mywebsite.com/addins/cesium/Build/Cesium/Cesium.js:23:3247694)
The above text plus the following are displayed in my debugger’s output window:
An error occurred in "CesiumTerrainProvider": Failed to obtain terrain tile X: 0 Y: 0 Level: 0.
An error occurred in "CesiumTerrainProvider": Failed to obtain terrain tile X: 1 Y: 0 Level: 0.
When using the unminified version, the two “Failed to obtain terrain tile” messages (shown above) are displayed in the debugger’s output window, there aren’t any references to the “array length”, and the map area is rendered showing stars but not the Earth.
I started to upgrade from 1.63.1 to 1.111, but it looks like that’ll require significant changes to the existing code.
Has something changed in the tile provider(?) that could be causing this problem? My code has been dormant for years (at least since 2022, but more likely since 2019).
Thanks!