Resource Save hanging on just one resource

As an example - this line causes the resource to fail saving:

<p><img src="/assets/uploads/file-name.jpg" /></p>

also so does this:

<h2 style="text-align: left;"><strong>Our <a href="[[~2]]">next concert</a> is booked for:</strong> Saturday 25th June 2022</h2>

But if I take out the ‘style’ tag - like this:

<h2><strong>Our <a href="[[~2]]">next concert</a> is booked for:</strong> Saturday 25th June 2022</h2>

it’s fine!

So inline styling, and img tags are cuasing it by the looks of things?!
I’ve pasted the content ino a new resource for testing - the same thing happens.
I’ve also pasted the content into a plain text editor just in case there were some spurious characters but nothing!