Define "bulky".
I have several machines that get all timid when they see 7 layers of denim with folds in it. A couple others that say: "Wait, did I feel a bump somewhere"? Some are Singers, some Kenmores, and one a 104 year old Minnesota Mdl B.
I've found that with bulky seams I have to reduce the presser foot tension. I was going the other way and the machine objected by staling out.
Also I was told to use normal sized needles rather than real large ones too. It seams the larger ones take more oomph to be pushed through the fabric layers.
And .... when was the last time the machine was thoroughly cleaned and oiled? The friction from a dirty machine that needs oil will slow it down a lot.
Joe