"I then set the progress bar "progress" to Player.playerHealth afterwards."
How long afterwards? Do you mean as an action directly below in the same on start of layout event?
If you take out the OR for progress and keep just the health condition, does the issue still occur? If not then its because you've set progress bar to playerhealth too late, after the check has taken place. If health changes to 0 on start of layout then thats fine, where you set the progress to player health may matter.
Also note that when I say later I mean this could be the next tick, so not even visible to the naked eye, Your values may appear to be correct wherever your progress bar event is but when the check has taken place to kick off the 3 second timer, this could've been a split second before.
Of course this is just speculation as we cannot see your event sheet.