Spreadsheet Slow on Apple Mac

I’m working with data tables with LO on macOS 15.6.1. Each file has 3 – 4 sheets, each sheet contains 4-6 columns with around 3400 data points. The file sizes are roughly between 5 and 16 MB.

Simple arithmetical operations within a given sheet are being carried out and sometimes use a number from a different sheet. Sometimes data plots.
It is now taking as long as 4 (four) minutes to save the files. I’ve removed the graphics but this doesn’t seem to help. The file size doesn’t even drop by very much.

What the heck is going on?

Any ideas?

Ask/Guide - How to use the Ask site - The Document Foundation Wiki #More_details