Hyperlinks don’t (always) stay linked

I have just been linking some text in a content block, but the hyperlinks keep disappearing. I highlight the text, click in the URL field*, paste the URL, click the update button** and all appears to be fine. But as soon as I click on the next bit of text to select it, what I’ve just done disappears. See this 20-sec screen capture.

It seems to be OK if I pause long enough for the page to update, but that makes doing a list of links a bit tedious. I guess I should be preparing all my content outside of the PageBuilder editor and then pasting it in.

Also on hyperlinking, it doesn’t seem to be possible to edit a link that’s already been done.

* It would be lovely if it was possible to paste immediately rather than having to click
** I expect to be able to press Enter, but that doesn’t seem to work