Broken LaTex if not in block mode:

$f (x) = \left\{ \begin{array}{ll} 5 & x \geq 0 \\ 23 & \, \textrm{sonst} \\ \end{array} \right.$

This cell contains more text following (rot) and (blau) resp. but it is not displayed. When published, these two lines vanish completely

(rot) mit der Ableitung

(blau) - bei $x=0$ ist $RelU$ nicht differenzierbar.

Inline LaTeX is not rendered if there is a space before the closing sign:

$f(x)$ vs. $f(x)$

This error vanishes when blank lines are inserted before the first and after the last $$

Proceeding from the last to the first layer, we redefine $$\delta_B=\delta_1\cdot w,$$ $$\delta_1=\delta_B\cdot \sigma'(z).$$ where $w,z$ is the matrix of weights resp. the $z$-value of the current layer.