Preventing long-press button function on DFPlayer board
Try this. Play with component values. Node 1 to the pin on the DFPlayer.  Sw1 is your switch. Normally the switch is closed so the transistor is off and the node 1 pin is internally pulled high (vcc). i.e. no input. If sw1 opens the transistor turns on and node1 is pulled to ground since the cap does not initially have any charge. Over time r2 charges the capacitor and Node 1 will eventually return to high Vcc. R2 and C will set the short duration time.



Correction : Move R2 to between the emitter of Q1 and the capacitor. The DFplayer data sheet does not give enough info to say if this will work but if you make R2 small (Say 2K to start with) and R1 big (say 10k to start with) it should work okay.