Created attachment 154064 [details]
TextBoxRotation20°_plus_VerticalText270°.pxx demonstrates the error
Open attached document. It has on the left side a shape with text. The text is vertical by the option "Rotate all text 270°". The textbox itseslf has a rotation of 20°. The red rectangle indicates the position of the textbox. On the right side is a screenshot of how it looks in PowerPoint.
Error: The textbox is not rotated.
The reason is in https://opengrok.libreoffice.org/xref/core/oox/source/drawingml/textbodypropertiescontext.cxx?r=e7c0bc48#110 where the value is simple assigned to moRotation instead of being added, and so overwrites the textbox rotation from #97.
[There are a lot of errors in that area, therefore I will not fix it immediately but together with the other problems.]
Also reproduced in
Version 18.104.22.168.alpha0+ (Build ID: efca6f15609322f62a35619619a6d5fe5c9bd5a)