cdj1000 mk3 weird noise and plays tthe previous song after a minute or two

its a weird thing i know, i should explain first that the equipment is old maybie a year and a half i bought it second hand and it wasnt used as much

i play 2-4 times a week for alot usually from 11pm to 7am then i stop and continue at 7pm till 7am,they work fine and have allways been,but after one humid night since i play outdoors one of  the players started skip the song but to the song before

if i dont put a cd in it starts goin from track00 to 99 97 94 90 ect.

now the thing is it depends on the day i still play on "hard mode" since i dont have alot of time till it stops playing and either stars shifting songs or just restarts the song its playing

it has a lot of sentimental value and i dont want to buy a new one cus im thinking of getting a rithm machine and synths but thats not the point,

does anyone acctualy know how can i stop this i think it may be the little motherboard where the button for the prev song is but idk i may be wrong

and i forgot to mention the other one works perfect.. thats why its bothering me