Description:
(Sorry dont know the english term for minimap used in impress. In German its "Folienbereich". I am talking about the small Thumbnails pictures of the slides)

Impress draws small images of the slides (both during editing and during presentation) which sometimes does not render all elements. 
A high chance (but i found no 100% reproducible path) for this error to appear is when a cursor is placed inside a text field.

Steps to Reproduce:
1. create text field 1 => its shown in minimap
2. create text field 2 => its shown in minimap
3. put cursor inside text field 1 again

Actual Results:  
sometimes: minimap does not show text field 1 anymore

Expected Results:
Minimap always shows an exact representation of the slide


Reproducible: Sometimes


User Profile Reset: Yes



Additional Info:
Also in presentation mode sometimes whole images are missing in the minimap/preview.
Happens both in 5.4.5.1 and 6.0.1.1
I also have a presentation which reproducible does not show an image in the minimap. Unfortunatly it contains confidential and the error disapear when i modify the slides to remove the secrets.


User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:59.0) Gecko/20100101 Firefox/59.0