I have had a Huawei P8Lite (2017 version) from new and despite it being
stuck on Android 7 I have never had any problems with it - until now.

For reasons various I have four email clients on the opening screen
(page 2) - K9-Mail, Gmail, Bluemail, and (Android?) Email - and have
never had any issues until a few days ago. If I open any of the clients
- they each open in one of their email addresses (i.e. not unified view)
and show me the last 20(?) email headers. If I select one mail the
client will open a new page with two lines of text in a box, these being
the subject of the email and the name of the sender with a reply (left
curved arrow) and the three-dot menu access. If I touch the box anywhere
the client close instantly. Similarly if I do nothing with the page of
email headers mentioned above, about five seconds after opening the
client also closes of its own accord. Most other apps work properly -
e.g. W3W works but Highways England just goes to a blank grey page then
shuts down a few seconds later and they are on page 4.
I have five pages (not all full) of apps where some work such as
Waitrose but others like ISS Detector on the same page do not.

Does anyone have any idea what could be causing this and how to fix it?
The only change I have made recently is to follow Google's instructions
of how to revert Chrome to its pre-2024 display format which went
smoothly and doesn't seem to have any time correlation with the mail
issue starting up. I have done PoR several times to no avail.