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?

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?