[Plugin: Google XML Sitemaps] Auto creation not working

My XML-Sitemaps plug-in for WordPress has stopped working properly and I don’t know why. When I try to view my Sitemap I get the error:

XML Parsing Error: no element found
Location: https://www.techietalk.co.uk/sitemap.xml
Line Number 2281, Column 1:

If I look at the plug-in options page I get the following message:

# The last run didn’t finish! Maybe you can raise the memory or time limit for PHP scripts.
# The last known memory usage of the script was 29.75MB, the limit of your server is 96M.
# The last known execution time of the script was 2.15 seconds, the limit of your server is 30 seconds.
# The script stopped around post number 379 (+/- 100)

What could be the cause of the problem? If I choose to manually rebuild the sitemap it does so without any issues. It only seems to be when I publish a new article and the Sitemap re-builds automatically. This is a big problem because I can’t manually update my Sitemap every time new content is added as I’m not the only author.

I see lots of these posts but none have been resolved, anyone know of any other XML generators that works reliably?