Custom CSS issue

Hi Tobias, sorry to bother you but this has me stumped. I’ve used your custom CSS facility for years without a problem, to do simple things like change background colour for certain cells. What is weird is that I’m now finding that, for two different tables on the same page, the same custom CSS (see below) works for one table (table 6) but not for the other (table 7). I can see from developer tools that the reason is that this is because the css for table 6 is getting included in https://thakehamparish.co.uk/wp-content/tablepress-combined.min.css
whereas the css for table 7 is not. Yet when I preview table 7 via Tablepress, it formats correctly.

Picking up clues from previous support threads I have looked for a solution involving css minification (cache flush etc), but I have no css mini plugin installed, nor anything of that sort via my cPanel, nor can I find any css minification options within the WP theme (Manta). My best theory is based on the fact that the problem only affects custom CSS that I have created since changing WP theme to Manta, which suggests that something obscure in the theme is interfering with new custom css code findings its way to tablepress-combined.min.css. Any thoughts you have as to whether this sounds the right track, and what to do about it would be much appreciated. (Obviously, change theme is a possible solution, but with quite a lot of investment in the current theme, I’d prefer if possible to avoid that!)

Thanks in advance.

=================
[Custom css in question below; code for table 6 works, but duplicate code for table 7 doesn’t, and the extra bit at the bottom for column width in table 7 is also being ignored, although it appears correctly in the tablepress preview]

.tablepress-id-6 .row-2 .column-9 {
background: #DCDCDC;
}

.tablepress-id-6 .row-3 .column-9 {
background: #DCDCDC;
}

.tablepress-id-6 .row-2 .column-13 {
background: #DCDCDC;
}

.tablepress-id-6 .row-3 .column-13 {
background: #DCDCDC;
}

.tablepress-id-7 .row-2 .column-9 {
background: #DCDCDC;
}

.tablepress-id-7 .row-3 .column-9 {
background: #DCDCDC;
}

.tablepress-id-7 .row-2 .column-13 {
background: #DCDCDC;
}

.tablepress-id-7 .row-3 .column-13 {
background: #DCDCDC;
}

.tablepress-id-7 .column-1 {
width: 16%;
}

.tablepress-id-7 .column-2 .tablepress-id-7 .column-3 .tablepress-id-7 .column-4 .tablepress-id-7 .column-5 .tablepress-id-7 .column-6 .tablepress-id-7 .column-7 .tablepress-id-7 .column-8 .tablepress-id-7 .column-9 .tablepress-id-7 .column-10
.tablepress-id-7 .column-11 .tablepress-id-7 .column-12 .tablepress-id-7 .column-13 {
width: 7%;
}

The page I need help with: [log in to see the link]