GPS relies on very very accurate timing. I would wager that the timing side of GPS is used more than the positioning side - but I have no way of confirming that.

Accurate timing is needed for banks accepting/sending payments (not just £5 for the window cleaner - more billions flowing every day).

That makes the issue worse as the actual app/device likely just relies on querying some NTP pool for accurate time. Then that would mean the actual stratum 1 servers are not working right.

I wouldn't be surprised if financial institutions use GPS for time keeping.

It's more accurate than getting it from a NTP pool.