Unless you are using a tram at Wimbledon, where it all goes out the
window.
I've had no problems at Wimbledon. What problems have you had?

No, I have not had any problems - I was just, perhaps a little flippantly,
pointing out that whilst there is a very simple rule for Tram use, it turns
into something that requires its own FAQ on the TfL website as soon as you
get to Wimbledon.

If you could share the details of the specific problems you've had
then we could try and work out what's going on, i.e. what were your
start and end points, what route did you take, did you have a
Travelcard on your Oyster, what time of day was this and what makes
you think you were overcharged - did you get the £4 max cash fare
'penalty' and if so was this applied once or twice?

What frequently happens is that my journeys seem to "start" from a station I
visited earlier in the day, but not the actual start of this particular
journey.

For example: I travel West Hampstead NLL to Richmond and exit.
Then Richmond to West Hampstead to change to Jubilee to Baker Street (or
anywhere really).
Then Baker Street back to West Hampstead to catch Thameslink northbound (not
on Oyster).

However, the journey history often looks like this:
West Hampstead NLL -- Richmond.
Richmond -- West Hampstead NLL
Richmond -- Baker Street
Baker Street -- West Hampstead

It seems to "miss" me entering West Hampstead jubilee line, and presumes
that I went back to Richmond to start a second journey somehow. This happens
incredibly regularly, but not always at the same stations - and on one
occasion I had *three* journeys starting from Richmond in a row. I don't
even understand how the system could, knowing that I have just travelled
from Richmond to WH, think that I have managed to hot foot it back to
Richmond in the time it takes to cross a road to start a new journey.

The gates always let me through at WH LUL, so I am not totally convinced by
your statement that as long as the gates open, all is well. Thankfully, the
majority of the time, my Oyster has capped (with YPR) for the day, so whilst
I am not overcharged as such - if anyone were doing these journeys without
the discount capping they could conceivably get charged for two journeys
when they only actually made one. Any advice welcome!

From observation this seems to happen quite a lot, and has been
commented on here before. It's nothing to worry about - if the gates
have opened then you're fine. One likely explanation is that the
Oyster reader on the gate is reading your Oyster card for a second
time and then obviously rejecting it, because it has already just read
it, validated it and opened the gate for you

OK, that may be right. I had wondered if it was connected to the fact that
my Journey History was all over the place, thinking that I was in Richmond
etc. and was trying to tell me, but was opening the gates anyway. I suppose
I ought to look at the gate code next time.