Updating for tracking purposes: the solution was to remove the Tobii folder and then include the latest SDK. Another part of the problems experienced was caused by the fact that @joostbos updated Unity to a version that, unlike previous ones, did not include OpenVR package. But, after seeing the warning and installing OpenVR manually, everything worked fine so we can consider this solved.
On our end, we have updated the documentation with a warning regarding deleting the folder before updating to a newer SDK: https://developer.tobii.com/vr/develop/unity/getting-started/