[MC-96553] Book score fail on half slabs

Player using book to 'cast' click on a score command targeting themselves does not work on half slabs. More correctly updating score with book fails between elevation of y@.50-y@.56 (y@=full number in the y axis).
Have tested this bug as far back as the chain and repeat command blocks were added and always fails.

Below are commands to replicate:
Book:

/give @p written_book 1 0 {pages:["[\"\",{\"text\":\"Bug testing \",\"color\":\"dark_blue\",\"bold\":true},{\"text\":\"\n\",\"color\":\"none\",\"bold\":false},{\"text\":\"Test \\\"Click Cast\\\" below on half slabs. \",\"color\":\"dark_green\"},{\"text\":\"\n\",\"color\":\"none\"},{\"text\":\"Click Cast\",\"color\":\"light_purple\",\"clickEvent\":{\"action\":\"run_command\",\"value\":\"/scoreboard players set @p[score_mana_min=2,r=0] CAST 1\"},\"hoverEvent\":{\"action\":\"show_text\",\"value\":{\"text\":\"\",\"extra\":[{\"text\":\"expect text \\\"Cast test successful.\\\"\",\"color\":\"red\"}]}}}]"],title:Halfslab Book Bug Test,author:RCvie}

Objectives:

/scoreboard objectives add mana dummy
/scoreboard objectives add CAST dummy

Mana score:

/scoreboard players set @p mana 100
/scoreboard objectives setdisplay sidebar mana

Command Block chain on repeat:

/execute @a[score_mana_min=2] ~ ~ ~ /scoreboard players remove @p[score_CAST_min=1,r=0] mana 2
/execute @a[score_CAST_min=1] ~ ~ ~ /say @p Cast test successful.
/scoreboard players set @a[score_CAST_min=1] CAST 0