Yes, it happened to all pages and all vaults.
I did not use any external plugins, just a customized CSS.
But I can remember it happened when I was modifying the following page. I added the last equation and then the math display function crashed when I previewed.
The last equation is very long and contains “[”, it probably leads to the problem. But the problem still exists after deleting it.
# Principal component analysis
## Purpose
To reduce the dimension of a matrix $\mathbf{X}$.
## Method
### Based on the covariance matrix
* Let $\mathbf{X}=U\Delta V^{\top}$ denote the [[singular value decomposition]].
* $Delta=\mathrm{diag}[\delta_1,\ldots,\delta_2]$ the singular values.
* $V\Lambda V^{\top}$ give a spectral decomposition of $\mathbf{X}^{\top}\mathbf{X}$ where
$$ \( \Lambda_{p \times p}=var{diag}\left[\lambda_{1}, \ldots, \lambda_{p}\right]=\mathrm{diag}\left[\delta_{1}^{2}, \ldots, \delta_{p}^{2}\right]=\Delta^{2} \) $$