Ehpro valkyrie deck won't stay on

[AdamMan]

Hey guys I'm not sure if anyone here has ever used it but I'm having issues with the ehpro valkyrie clone. I've already sanded down the contacts and the insulator and put petroleum jelly on the contacts and the switch to fix the hot firing button issue but now the deck won't stay on... it was perfectly fine at first but now the second the battery is in there it just pops right off and I'm not sure if that's a fix. Any help would be greatly appreciated!