What happened today, exactly?

Yes, I know that a signal at Embankment went on the blink, but does
anybody have any further detail? I suspect that if the heat wasn't the
cause, then it certainly didn't help.

Can anybody remind me where on TfL's website I can find the form to
claim for compensation, please?

I also wanted to ask a question about daily capping on Oyster cards.

I topped up my card with £5 last weekend at a Zone 2 station, thinking
that this would be sufficient for travel within Zones 1-2 for the day as
the Oyster card would automatically to cap itself. If £5 would not be
sufficient, then I could simply top an extra pound or two. But I was
certain that I would cap out.

I took the tube into town, and then later in the day jumped on an NR
train at Waterloo for Vauxhall, where I changed to a Victoria line train
for Brixton. Lo and behold, I find at Brixton when I tried to use a bus
that I did not have enough money.

So, I topped up my card with another couple of pounds and was able to go
on my merry way. But later, I found that I again did not have enough
cash to use the tube at Elephant & Castle, forcing me to once again top
up an additional £2.

Where did I go wrong? Even if I originally did not have enough on the
Oyster to get it to cap out at £5, I would have though that simply
adding an additional £2 would have been sufficient to let that happen.

Thanks for help and advice.