[TYPO3-english] Multiple images in content elements after upgrade to 6.2

[Tomas Havner]

Hi!

Last week we tried to upgrade our (large) Typo3-installation from 4.7 to 
6.2.17. We use the Dam-extension to manage our files.

After we had finished the upgrade wizard in the installation-tool. After 
a number of timeouts. We noticed that in image-, text-with-image- and 
filelist-elements the images and files had multiplied.

Not in the rte-editor but e.g. in the text-with-image-element under the 
image-tab there were 2, 3 och 4 identical copies of the images.

When we examined the sys_file- and sys_file_reference-tables there were 
one or more duplicate of most of the rows.

Luckily we did the upgrade on a off-line-server. But I would really like 
to know:

Has anyone experienced this?
Is it a bug in typo3 or have we missed something?
What can be the cause?
How can we avoid this?

Any comments are greatly appreciated

Tomas