I’m glad I’m not losing my mind, at least. I noticed this a while ago and just came back from a £30.01 shop - so naturally it triggered the self-service machine to decline the contactless despite Google Pay authorising it.
Shop assistant swore blind they never accepted over £30, but I know I’ve done large shops there before.
The problem is their Pay+ app (which they’re clearly trying to push people towards) is rubbish - half their tills don’t scan the barcode correctly, and it keeps logging me out and refusing to accept my password. I use Lastpass so it’s clearly something on their end corrupting it.