FlashForge printers come with a heated bed (good!) and a scarper tool (good!) made of metal (good!) that is electrically conductive (...) as are the EXPOSED BARE SOLDER contacts (not good) of the 24V bed heater. If the metal tool happens to touch those contacts while the heater is on...
...bad news for your main board. Fortunately, there's a solution in the form of a plastic protector. Simply print this out of PLA (use the model with hole unless you have translucent filament; the no-hole printed translucent looks amaaaaazing!!!) and clip it onto the back of your heater board. It goes on a little hard, so you'll want to support the bottom of the circuitboard with your thumb so as not to break it.
This was designed for a FF Inventor; I do not know if it will fit other FF printers but you are free to remix and share. I took up the problem with FF tech support, offered them this design, and explained how a few cents worth of plastic could dramatically improve customer satisfaction, but they weren't interested. Since then, I sold my TrashForge (good riddance!) and got a second Creality printer and a Prusa.