Photo not bad, and I note you are connecting Vo - pin 3 - directly to ground and the contrast is just fine. You may be getting some “sag” on the USB supply voltage which drops the contrast voltage to an optimum level (about 4.7V) by default.
Also note brightness limiting resistor of 220 ohms. If your LCD has R8 or R9 as “101” - 100 ohms - as it almost always does, you do not need such a resistor but if you wish to limit current consumption, that is OK.
What I would suggest regarding your actual problem, is to put a 10 or 47µF capacitor on the breadboard directly across pins 1 and 2 of the LCD. Also wiggle your power connections to make sure they are making good contact.
My son is building a Hollywood style bomb which has a counter (in the display)
Just don’t accidentally leave it in any supermarkets!
I also attached the code which shows how it’s working now. The display problem does not exist in the project currently, because the LCD is turned off during the sound. Hopefully all this gives a better picture what is going on. Thanks!
I find it very inconvenient to look at code in a “.ino” link. Much more appropriate in the post itself using “code” tags - the little “scroll” icon.
Suspect the text should be “DETONATION IN:”