# Using makecell in tabu: incompatibility with the packages tcolorbox and todonotes

I have a problem when using the package tabu with makecell and tcolorbox and todonotes. This is my minimal example code:

\documentclass[a4paper]{scrreprt}
\usepackage{tcolorbox}
\usepackage{todonotes}
\usepackage{tabu,makecell}
\begin{document}
\noindent \begin{tabu} to \textwidth {@{}lXX}
normal line & A & B \\
line with makecell & \makecell[tl]{A\\C} & \makecell[tl]{B\\D\\E}
\end{tabu}
\todo{To Do: ...}
\end{document}


When I exclude the line with \makecell, everything works. Also when I exclude the packages todo and tcolorbox (and of course, the line with \todo command, but keep the line with \makecell), everything works.

The problem occurs when I include at least one of the packages tcolorbox or todonotes. Then I got the following error:

./test-tabu.tex:9: Improper \prevdepth.
\tabu@verticalspacing ...tempdimc \the \prevdepth
\@tempdima \dimexpr \ht
\t...
l.9 \end{tabu}


Also the solution from tabu: Error since update didn't help.

Does anyone know how to fix this?

Here is the first line of the log file:

This is pdfTeX, Version 3.14159265-2.6-1.40.19 (TeX Live 2018) (preloaded format=pdflatex)