Strange text on MAX7219

I have put this project together:

And it kind of works, except I cannot make any sense of some of the text, as per the 2 pictures.
In my case, the left hand white button makes then text brighter, and the right hand black button makes the text dimmer.

The middle yellow button seems to do most of the operations, ie scrolling , stopped, next etc. It is in this mode where the text looks not readable.

The code/sketch uploaded to the arduino bhoard with out any errors.

Thanks

MAX7219_RTC_dht11.ino (12.6 KB)