Products with over 5000 combinations

[Claude L.]

Hi, 

We have a live 1.6.1.18 store with +/- 100 products, some of these products have over 5000 combinations, everything is working fine, front and back. Server info is : Intel(R) Xeon(R) CPU E5-1650 v2 @ 3.50GHz / PHP 7.1 - max_input_vars 30000 / memory_limit 512  / Version de MySQL 10.2.30-MariaDB

Lately, we decided to upgrade to 1.7.6.7 in order to use Creative Elements module. We cloned our 1.6 shop on another server, uninstalled the theme and all modules, upgraded to 1.7 with 1-click.  Server info : Version de PHP : 7.1.33 / Limite de mémoire : 4096M / Temps maximal d'exécution : 6000 / max_input_vars : 190000 /  Version de MySQL : 10.2.32-MariaDB 

Now, on the front, everything is working fine but in the back-office, i can't open my products with alot of combinations, some can open but are unable to save, the bigger ones give a HTTP ERROR 500.

Am I missing something ?