upgrade 4.7 to 5.2

I try to upgrade my 4.7 version to the 5.2. (local try for the moment)

Everything seems to work except the taxonomy module :

Instead of seeing the terms of my categories, they are all transformed into the word "array".

I checked if the terms have not been modified during the upgrade but in the administration pages concerning category, all the vocabulary and terms are still there...

I tried to erase some terms and create them again but the newly created term appears as "array" after publication.

Anyone has heard of such a problem ?

Thanks

Benoit