Did a little digging in MySQL...
When only the first condition is applied (highlight new tickets in the last 1 day in light green), the ost_queue table shows the following:
"conditions":[{"crit":["created","ndaysago",{"until":"1","int":"d"}],"prop":{"background-color":"#72ee72"}}
When the second condition is added, the table cell shows the following for the first condition (notice the number "1" is missing):
"conditions":[{"crit":["created","ndaysago",{"until":"","int":"d"}],"prop":{"background-color":"#72ee72"}}
If I manually add the number "1" back into the table cell value, it applies both conditions as it should. So it seems there is an update somewhere that isn't keeping the first condition's value.