Symbol 2D block

[CliveD]

I have been having a problem since upgrading from V9.5 to X3,X4 & X5.
When I replace Chiefs symbol 2D block with my own it loads in at approx 2.5 times the drawn size.
The attached file shows my problem.
(1) I have placed an electrical sw. and changed its 2D block for my own (Drawing standard here in NZ & Australia).
My block is shown floating, the sw plan block shows at about 2.5 times my block size !!

(2) I have also placed a wall power socket and changed to 'our' cad block, again about 2.5 times size. Also have a problem with attachment to the wall being wrong, got it right for the sw. but cant remember how ?

(3) I have inserted a Chief Core Cat wall basin and changed it to 1 of my cad blocks, same result.

(4) Finally if you examine the roof planes the ridge caps have been edited to my ridge cap (copy inserted in plan)

Can anyone tell me what I'm doing wrong please

Hoping for lots of good advice