New theorem produces 404 not found error for proof notebook

[wdcraft01]

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It's not clear how consistently this error arises, but over the past few months we have seen 404 not found error when initially trying to access the proof notebook for a newly-generated theorem in a package's theorem notebook. The error seems to arise in the following steps: (1) a new theorem is defined (in a pkg theorems nb); (2) the theorems nb is "re-run,” i.e. the kernel is restarted and all the nb cells are re-run from top to bottom; (3) clicking on the new theorem's linked label produces the 404 Not Found error. If the kernel is restarted and the nb cells re-run a second time, then clicking on the new theorem's linked label works as it should and takes the user to its proof notebook just as expected. @wwitzel wondered if perhaps the error was arising because the clicking on the linked label was happening before the theorems notebook was finished running, but this does not appear to be the issue (that is, the error occurs well after the theorems notebook is finished running).