We did the exact same thing. My wife failed the A1 test in the Landmark Hotel in BKK. I told a friend and he said that his wife had the very same problem at the same hotel a year before so he flew her over and take the test on a holiday visa. I made the point to have my wife do the same when she came over for the first time for a holiday, meet the family etc and she passed quite significantly.
Then Covid 19 happened. When we came to reapply she took the test again at the Landmark. She failed again but they didn't explain why. I complained informing that that she had passed in the UK 2 years before and was told that they don't have to, to which I replied, what is the point of having the section for "feedback" on the form? The London test centre gave feedback but I couldn't find it as evidence to strengthen my argument for a free retest. My wife then flew over the next month, passed the test with distinction.
It's almost like the people at the Landmark are out of touch but the people in London have a better perception of what is actually required in the UK. Though writing that my mum tells me her local Tesco store is currently full of Tesco employees who tell her they "don't speak English" when she wants to ask them something so she's miffed that her daughter in law has to go through so much trouble.
It's annoying but taking the A1 test in the UK, or at the very least avoiding the Landmark Hotel is worth considering for spouse visas.