If you have at some point uploaded a new version of the BUILT-IN plugins, we recommend taking the following steps before updating to 1.2.0.
1. Pause all workflows.
2. Select any built-in plugin bundle that was NOT uploaded by a user, and make it the active version.
3. Delete any built-in plugin bundles that were uploaded by a user.
4. You may now update to 1.2.0.
To clarify, this is only an issue if you got a bundle from us for an update of the BUILT-IN plugins. Uploading any number of CUSTOM plugins will not require any special attention in update, and they can be left in place during the update.