CB Subs plan content access errors on Joomla 3.7.2 upgrade

upgrade Joomla from 3.6.2 to 3.7.2; Cb 2.1.2, CBSubs 4.1.0

I have two sub-categories of the same category, ID 27 and 37. I need to restrict access (via menu items) to 37 but not to 27. This worked fine in Joomla 3.6; after the upgrade it behaves oddly;
If I set my plans to restrict access to cat. 27 it works fine; I can access 37 from its menu item but not 27 unless logged-in as a plan member.
If I set plans to restrict access to cat. 37 I cannot access either sub-category and get redirected to the registration page from both menu items.

So you can't access 27 if only 37 is protected? Are you sure there are no plans protecting 27 during your test? Is 37 a sub category of 27? Are you protecting the category it self or just the menu item? I recommend protecting the category it self as menu item protection is entirely based off Itemid in the URL.

That's right; protecting 37 also protects 27, but not the other way round, which is what i want. The two categories are sub-categories of a main category. I am protecting the categories, not the menu items;
I am now testing the various results by editing the database in MyphpAdmin, to be able to check that the 4 plans: I have are identical [apart from the pricing]

I have just tried duplicating the category ID 27 and creating a menu item for it, and re-allocated one of the articles to the new category ID 112; all plans have 37 protected, but not 27 or the new one.
I now have access to category 112, with its article; but still have no access to category 27. I also created a new menu item for category 8; I have access to that too, so it seems only 27 has the problem.

Strange, I've no idea what could be causing that. When trying to access 27 is it showing the plan for 37 or is it showing no plans but with the message that they need to subscribe? Typically the best way for CBSubs to protect a category is to specifically select that category and then ensure that category is set to Public access otherwise you maybe hitting Joomlas access permissions if as a Public users you're trying to access a category only accessible by Registered.

I have now replaced the protection by category with that by menu item and the problem is gonel I now have the behaviour I want, access to 37 reserved for plan members, but 27 available to all. there has to be some configuration error somewhere but I can't see any; and I'm sure that this category problem did not exist before updating to Joomla 3.7.2 from 3.6.x