While my CUT is different make, the setup seems the same.
The lever goes thru a plate attached to the 'tunnel' via 2 machine screws.
With the screws loosened the plate can be 'repositioned' to make for a proper adjustement.
The holes in the plate will be oversized in relation to the machine screws that hold it in place, allowing for the adjustement.
Since 'low' is not fully grabbing then the plate needs to be slid towards the low setting to make for full engagement.
It does not take much movement to reposition the fulcrum point, maybe a mere 3/32".
I have, over the years, needed to reposition both my
PTO lever as well as my
4WD engagement lever as vibration (and maybe my size 12's) tend to loosen and allow these levers to go out of alignment.
Hope this helps, and good luck.
When you shift to low, do you feel a 'click' to confirm the ball/spring dedent is working?
If yes then the adjustement proceedure should correct the situation.