I honestly suspect that there's a shortage with one of the components that they spec'd for that model. Otherwise I'm at a loss to understand why that one model is a problem.
As before this isn't aimed at you, but as a company why are you not pushing Asus for answers? You've sat on over a million pounds of pre-orders for that one model and no one even bothered to ask why the amount of stock in 3 months for it is in the single digits?
If a supplier is causing a delay for my customers, I don't get to shrug my shoulders and say "too bad I have no idea". I have to escalate, I have to speak to them and find out what's going on.
If I did the following I would lose my job:
"Why has an engineer not been around to restore my service which has been down for 12 hours"
"DUNNO LOL"
What I actually do:
"I've just checked for the latest update which was 2 hours ago, let me call the supplier and then I'll immediately call you back".
[10 minutes later]
"I've just spoken to the supplier who've confirmed the delay is because the replacement component isn't in stock in the region, so they've had to ship this down from a depot in Glasgow. This is due to arrive with the engineer at 20:00 so we hope to have the engineer on site for 21:00 subject to traffic."
After 3 months of essentially nothing, I would be raising hell with Asus. If you guys can't get stock, it's your job to get answers for your customers.
Alarm bells should have been ringing when other models came through the door and the Strix has had nothing. It doesn't seem to have even been considered.