Hi patvandenbosche
It's issue of JAEM component, not T4 or JA Blockk template. Our developer is working on this to fix the issue.
If you want to update template now, pls try this way:
1/Backup your site first
2/Backup this folder: /templates/ja_blockk/local/etc/layout/ - you may copy JSON files in this layout folder to somewhere in your PC
3/Update new version of template via JAEM
4/Copy the JSON files you backup in step 2 to: /templates/ja_blockk/local/etc/layout/
These JSON files store the settings in template.
Regards