X carve carve wrong

Hi,
My x carve go fine for the most off the thime ,

But somethimes when i should Cut out the parts , its
Going fine in the beginning , but when i come down in the material
Its just dig in too the wood somewhere else and destroy the material
And a waste off thime.

My reflection of theese problem is that in the track where the bits
Should walk collects a lots of saw dust ( i am not having a good dust collector yhet) when i blow the dust out of the track it seems to bee good all the thime.

Can that bee My problem , or am i just having luck that thime i have blowing
Out the dust from the track ?

Or can My belt bee too lose ?maybe stretch it a little moore, i havent stretch i,
Just did that when the machine was new about 6 month ago.

Other Than that the machine works great, nerver had any missing steps or so.