Problems with image cache in Android

1 step - I access the application after that I open a course. Image 1

2 step - I go to the panel and reopen the course. Image 2, notice that the figure at the beginning of the text is broken.

The same happens if after step 1 I simply pull the screen to update.

If after the problem I access settings > synchronization and synchronize (image 3), the image will be shown again when I access the course. However, if I perform step 2, the image will disappear again.