Heatmap Time Sorting Issue

I recently created a weekday and half-hour heatmap using Beast Mode functions to break timestamps down to half-hour increments. But for some reason, the chart is sometimes sorting the half hours into the wrong order.

Notice how 3:30 PM appears before 3:00 PM in the chart below, as does 830 PM before 8 PM and 930 PM before 9 PM:

The source columns I'm using to calculate the half-hour intervals are datetime columns, and the formula I'm using to calculate half-hour increments is:

TIME_FORMAT(CONCAT(HOUR(

case

when `Call ID` is not null then `Call Create Date`

when `Comments ID` is not null then `Comment Create Date`

when `Chat ID` is not null then `Chat Session Start Date`

else `Ticket Create Date`

end

), ':',

CASE

WHEN

FLOOR(MINUTE(

case

when `Call ID` is not null then `Call Create Date`

when `Comments ID` is not null then `Comment Create Date`

when `Chat ID` is not null then `Chat Session Start Date`

else `Ticket Create Date`

end

)/30)*30 = '0' then '00'

ELSE '30'

END

),'%h %i %p')

And the Beast Mode formula I'm using to calculate Interaction Hour Is:

hour(case

when `Call ID` is not null then `Call Create Date`

when `Comments ID` is not null then `Comment Create Date`

when `Chat ID` is not null then `Chat Session Start Date`

else `Ticket Create Date`

end)

Then I sort by
Weekday, Interaction Hour, and Interaction Half Hour in that order.

Any ideas what could be causing the sorting issue?