CB field with CB Conditional shown on and off in edit mode

I implemented the fix, tested it, and can confirm that the issue with the SQL condition is fixed. Thank you for that.

But... I now completed my setup for this field 1, and added the second condition, which is simply 'AND this field 1 is not equal to yes'.
So my condition is now: (SQL count resulting in 5) greater or equal to 5 AND field 1 not equal to Y

Result: the display or not according to the conditions, works still fine, the field 1 is displayed in my test case because it is equal to Y.
BUT when the user changes it from 'Y' to 'N' (or the opposite, didn't test that), that change is not stored in the database.
And when he changes a field 2 at the same time, that change to field 2 is correctly stored, but the change to field 1 not,
I don't get any error or error message.

Sorry, not understanding your condition setup. Please provide a screenshot of it. What type of field is this "Y" / "N" field? A checkbox field set to display as yesno buttons?

I understand. screenshots of all used elements of the field definition uploaded.

BUT when the user changes it from 'Y' to 'N' (or the opposite, didn't test that), that change is not stored in the database.
And when he changes a field 2 at the same time, that change to field 2 is correctly stored, but the change to field 1 not,
I don't get any error or error message.

Having a hard time understanding this part. So when the radio button is changed to N the conditioned field is hidden as expected? What isn't stored correctly here?

The goal of the fiels is to accept a maximum of 40 subsciptions (40 people who choose 'Y')
Once the goal reached, the field is correctly no longer shown, except to those who allready selected 'Y'. 
The issue is that once the 40 times 'Y' is reached, those who slected 'Y' before and now want to update their details and change 'Y' to 'N', can do that on the screen (still correct) but that change is no longer stored in the database. So next time they display or change their details, the 'Y' is back.

Are there any conditions on your radio field that's storing Y and N? Is there a reason you're using a radio field here instead of a checkbox field (this can be set to Yes/No buttons mode)?