[GNC] New tax year - unexpected GnuCash display

[aeg]

I'm using GnuCash Version 4.12 on Windows 10, and today, 6 April, is the beginning of the new UK tax year.
As I have the "Total (Period)" column showing in the COE, I was expecting to see mostly zeros in that column today, but was surprised to see many totals much higher than that, and in the region of what I might have expected if it had not been a new fiscal year.
Under Preferences/Accounting Period/Start Date, the selection is Absolute:6/4/23, and under End Date, the selection is Relative:Today.
In previous years, this arrangement has appeared to work as expected, and the only other change I've made since last year is an upgrade from GC 3.5 to GC 4.12.
Today, after a series of trial-and-error changes to the Preferences setup, each followed by a restart of the program, I've managed to get it working as expected, with the final setting the same was at the start. Although it now seems that all is well, I'd be interested to know how this problem might have occurred, and whether there is anything I should have done to prevent it, or whether there might be a bug in the program that others may be able to identify. Also, is there any possibility that other totals in that column may have been inaccurate during the last 12 months but were less easy to spot than they were today?

Regards,Alan