You are pulling close to 0.5 amps at 5v, which if powered from a USB source could be near limit. With switcher startup surge, make sure your 5v source can handle the peak current.
One of the most critical part is the inductor of the step up circuit. It needs to be carefully selected according IC datasheet.
Simple debugging tests are: measure 5V, 24V and the voltage across 33R whether they have the expected values and whether they are stable.
A DVM can give only raw (timing) informations, better use a scope.
You did use a 24V power supply circuit. It can't compensate for VF drifts (21.7V ... 24.5V). Why didn't you use a dedicated step up LED driver circuit?
Not related to the LED problem:
Don't use an inductor in the GND line of the LCD (L34). GND should be clean (low GND bounce), low impedance and should refer to a common GND level.
All signals (power, logic...) should refer to the same GND node.
An inductor in the GND line makes things worse.