IHC-200 HD cannot be set less than 10

Suddenly today, my unit is not functional properly. I use it to run a fogger in an orchidarium and have successfully been maintaining the humidity between 88 and 90% until today… I believe the issue is that I cannot set the HD (Humidification Differential) to anything less than 10. The manual says I should be able to choose a value between 1 and 20.

My current settings are: HS - 90; HD - 10 (cannot be set lower); DD - 10; AH - 99; AL - 0; PT - 0; CA - 0.

Am I correct that the issue is the HD and how can I get it to set lower than 10?

Hello,
If you press and hold the SET button, could you enter the setting mode?
If you switch to HD and press the up/down button, can its value be changed? Its setting range is 10%~20%?
Is there possible to take a video of this problem and send it to support@inkbird.com?
Thanks.