Daniel, Acorn,
Many thank for your assistance and knowledge. When this problem first appeared around 2017 or so, I didn't know if it was the software or my computer. I was running a fairly powerful computer back then. I have since replaced the computer with modern, powerful CPU, upgraded RAM... but the most boost came from replacing the old Spinning Hard Drives with Solid State (replacement justified by this Xara Processing issue). Unfortunately, after replacing and upgrading, I was still having the issues with "processing". Thus I am sure it's not the computer set up. I had assumed that because the issue was present in multiple versions of Xara, that it could be corruption in my file. Not unexpected as some of my files are old, large and have been opened/saved with subsequent versions of Xara. However, the problem abates for a time after rebooting. Hence, I am thinking it's a caching issue or I have reached the maximum size or number of vectors for the software.

In any case, when I experience this issue again, I will be sure to check the "Document Info" to glean any relevant data. If I do find that there is a Xara bug I will report it, If I find that it's something else I will update this thread for future searchers. I'll also keep an eye on repeated objects to see if this might be a source of issues.
Many thanks for your assistance,