Hi
Sorry to hear of your problem and record powers failure to resolve it thats unfortunate.
So down to the nitty gritty they are both not fit for purpose send them back and get a refund.
Second option is to get the threads checked out you need someone who can check the major diameter of the thread, if thats ok you need the effective diameter
Checking one way is to three wires of the correct size
These will give you the effective diameter of that thread . if this diameter is plus it will mean the thread will be tight if the diameter reading you take and is less than the stated diameter it will be loose.
This term effective diameter for any vee shaped thread
55 degrees,(whitworth) 60degrees (metric,unc,unf,anc,anf)and can be found in any engineering book ie machinerys hand book,zeus etc
Also get the thread form checked this can be tipped so the angle on each side of the vertical is not equal.
A tap that size will cost you the earth.
For all of this you can contact a local engineering shop
Good luck with it.