Hi!
Thank you very much for the details, it helped me a lot!
The problem there is that the ACF checkbox is a complex field, and is stored as an Object in the database, not as a simple text field. Like so:
[code]a:3:{i:0;s:1:"L";i:1;s:2:"XL";i:2;s:1:"M";}[/code]
So exact matching won’t work, as the whole text should be entered. The non-exact matching is not working because for example typing “L” matches this string even if only “XL” is selected, because it’s a substring of it.
I have done some experiments and I have found a solution. To match any of these, the delimiters (double quotes) should be added to the values as well. In your case, you need to change them to:
[html]"XS"||XS
"S"||S
"M"||M
"L"||L
"XL"||XL
"XXL"||XXL[/html]
So basically encapsulate every value with the code of the double quote string aka:
[code]"[/code]
This did the trick on my test environment, and hopefully for you as well 🙂