Rangefinder VL53L1X dist_bottom not valid

Hello,

We have issues working with the VL53L1X. It appears from the dist_bottom that its measurements are good and consistent with GPS measurements, however the dist_bottom_valid always goes to 0 when the drone is in the air. Also, while looking for clues in the log, I noticed that it does not report any rng_vpos values.

Example log: https://review.px4.io/plot_app?log=672d60a5-0d4a-466c-9b12-51763a44383d

Firmware is a slightly customized 1.15.3 which manually enables the driver on startup. The rangefinder is configured to work in conditional mode.

Any pointers would be appreciated!