The number 1 evaluates inside HoldForm sometimes

If I run the following code:

Do[
 Print["*** ", HoldForm[x] /. x -> a, " ***"];
 Print["Replace: ", (HoldForm[x] /. x -> a) /. {n1 -> 1, n2 -> 2, n3 -> 3}];
 Print["FullForm: ", FullForm[a]];
 , {a, {n1 n2, -n1 n2, n1 n2 n3}}
 ]

I get

    *** n1 n2 ***
    Replace: 1 x 2
    FullForm: Times[n1,n2]
    *** -n1 n2 ***
    Replace: -2
    FullForm: Times[-1,n1,n2]
    *** n1 n2 n3 ***
    Replace: 2 x 3
    FullForm: Times[n1,n2,n3]

I kind of understand what is going on, but I would like the output in the second case to be -1 x 2 and in the third case 1 x 2 x 3. How do I do that?

{n1 -> HoldForm[1], n2 -> 2, n3 -> 3}