Something wrong with my guitar

Already 2 of my guitars are broken due to the electronic side of things, there is a bit of broken wire where you put the lead in.

So i have another guitar , so because the other 2 are broken i had to use this and get some new strings, everything one fine, but the strangest thing is happening, on the bottom string when i play any play other fret apart from the 3rd its fine, but when i do play the 3rd fret, it sounds completely wrong and it sounds a little muted, in fact when playing the 3rd fret , its seems to sound like the same note as of the 5th note. Same thing applies to the second string. What the hell is wrong, never come across this before?

also if there's any websites on how to fix the wiring or something like that which will help me fix my guitars i will be grateful for you to send me some links

Thanks

my guitar did that, just open up the back and get someone to solder it and it should be fine