Like every 0.10 seconds of game time renew them?
Floating Text - Change the position of (Last created floating text) to (Position of (Triggering Unit)) with Z offset 10.00
Try to use this action, if that doesn't work try this
Floating Text - Change the position of (Last created floating text) to (Triggering unit) with Z offset 10.00
If that doesn't work, try his suggestion.
I'd reccomend every .03 seconds of game time for 33fps (i use this in my map wispwarz)