MAKITA JR3070CT AVT Reciprocating Saw ejects blades under pressure?

Hi, i have a MAKITA JR3070CT AVT Reciprocating Saw which when cutting sometimes releases the blade from the tooless chuck. i had the chuck apart and everything seems in order but i asume something has worn or broken and needes replacing but i cant see what.( saws not very old so cant think somethings worn) does anyone have any experience with this and maybe have an idea of which part is defective? thanks for any input in advance.