This is an odd problem which I had, then it went away, then in the last ?2 weeks it's come back. It also doesn't happen on every thread.
When I go to a new page, or a new thread, or jump into a thread from Notifications, the page is displayed correctly for a second or two but then it whips past all the posts to the end of the thread at top speed, & then it sits there showing me the last post on the page. If I'm reading through a thread this can happen on every page, which as you can imagine gets very wearing.
I'm using Chrome on a Chromebook.
e.g. it doesn't happen on this thread:
https://www.mumsnet.com/talk/property/5339779-caught-on-camera-neighbour-filling-up-my-skip?page=15
but it does happen on this one:
https://www.mumsnet.com/talk/am_i_being_unreasonable/5341324-to-cancel-dds-dance-comp-after-what-she-said-to-her-little-brother?page=8