The bookmark I made yesterday is still working OK. + deleted it, created a new one, and that's OK as well.
That (highly) suggests it isn't anything on the site, and most likely it's something local to your device that's causing it.
One other simple thing you could try (should have said yesterday) is to power it down/do a reset.
I can talk you through some stuff on a screen share if you have a Skype or Telegram account. Just pm if it gets to the point you want to try that and we can fix up ten minutes to try and work it out.