[Résolu] how to downgrade ?

Background of the issue:
last night I upgraded wp , wpml/wcml and few other plugins to latest version ,

today I noticed my wp sheet editor plugin goes dead slow import from csv

checked with wp sheet editor , concluded the WCML is causing the slowness , after disable WCML , thing goes back to normal

now how do I downgrade WPML/WCML ?

Symptoms:
None

Questions:
How can I downgrade WPML to a previous version?