Hi Medienor,
Be aware that a few weeks ago, Kirki was updated to version 4.0 which changes a lot of things. The developers of Kirki realised that this update caused some issues for many WordPress installations and they have cancelled the release to return to 3.1.9.
Therefore, the solution is to reinstall Kirki to get the 3.1.9 version. For that, I invite you to delete the plugin and reinstall it by downloading this version here: Kirki 3.1.9.
Be sure that the new version will be compatible with your theme as soon as possible. However, we have to deal with this compatibility once Kirki has released a stable version.
Let me know if this issue is solved when returning to kirki 3.9.
Best,