Fixing Hereflow lens

The lens on my Hereflow sensor detached itself from the sensor. What’s the best way to fix this?
See pic here:

You can glue it back(lightly touch on upper outer race), make sure that the glue does not touch the seat or the part of the lens(maybe use thicker glue).

We did reglue it and it seems to work, the measurement quality seems to be fine