I was in Troon yesterday and went for the 1436 back to Glasgow Central which was cancelled. I noticed nothing was coming south to Ayr. Station staff said that something (don't know what) had sat down at Cardonald and things were virtually at a standstill. The 1447 Troon to GLC had left Ayr but they weren't sure how far it would get - see later.
Passengers for Glasgow were advised to travel on the RT 1441 Class 156 to Kilmarnock and change there which I did. The Carlisle - Glasgow was running RT and a trundle across the platform saw me and a few others on board with a couple of minutes to spare.
But the signal stayed resolutely at red and with no working PA on the 156, the conductor walked through the train to announce there had now been a signal problem near Barrhead! (RTT has this as a points failure.)
We left 34 late eventually and arrived in Central 46 late; the last mile from Eglinton St taking 13 minutes because of platform congestion due to both Kilmarnock and Gilmour St lines being heavily disrupted. But from what I can see only the Paisley disruption was caused by a train fault.
The Glasgow Central concourse was rammed as few platforms were being displayed whilst control were juggling the schedules, stock and crews. Ironically, if I had waited for the 1447 from Troon direct to GLC, it was only 7 late into Central and that was because of platform congestion. It was one of the first to get through with only a small delay

. But after that there was nothing from Troon to Glasgow for over an hour.
Anyway nothing to do with Scot Rail, but the lightly loaded 1640 Pendolino south got to Carlisle about RT and then sat down there and had to be re-booted to clear the fault. Departing there 17L and steadily filling up at Penrith and Oxenholme, it gradually lost time, arriving at Preston 20L. I was just in time for a sprint under the subway to see the Northern Manchester stopper depart on time.
Never mind, the TPE from Glasgow to the Airport was RT (didn't fancy coming back on this all the way) and only 20 minutes away. But then the boards flashed up "Cancelled". No surprise; the cause was no crew to take the train onwards!
Luckily my delayed Pendolino had delayed the Edinburgh - Euston behind, so if it maintained its schedule I would have a cross platform connection at Wigan to the Alderley Edge stopper. It was nail biting as there was a delay for getting catering off at Preston but I made it with a couple of minutes to spare, And the Wigan - Alderley was RT throughout!
So 4 TOCs were involved and the only one without disruption was Northern!! An interesting day on Britain's railways...