P: Smart Collections containing Color Label criteria show "No photos in selected smart collection"

A bug is always general. On the same platform and for the same version, we are all running the very same code. Just, the bug may or may not appear depending on the way the software is used, depending on the system configuration, etc. So, it doesn't make sense to blame the user by saying that since others don't see the bug, the affected user must have a very specific configuration or have done something strange. That's the usual easy answer from lazy customer support departments. Hence the usual recommendations : reset your preferences, re-install the software, re-install your OS, etc. Which usually is a just a loss of time. What has to be done is to really diagnose the problem by finding what in the way the customer is using and configuring LR makes the bug appear. That would be useful.

Again, the bug appeared after installing version 7.3 (something I should have avoided). Nothing (hardware or software) had changed on my system. So, there's something new that must be spotted in LR, not in my system.

But the problem is that I can't reproduce the issue on my Mac, and somebody else can't reproduce it on their Windows PC. That means it has to be something that is somehow related to your particular setup, not a general bug that we all would see. 

Doesn't help.

As a former software engineer, I use to diagnose problems in a logical way. I can't do much since I don't have access to the source code. But...

What I see here is that LR is not able to properly count the number of items in a dynamic collection. That is, the Grid View has a problem with this. On the other hand, the Collections panel displays the correct number of images for that collection. So the Grid View obviously has a problem in this case (by the way, by far not the only problem with Grid View on a dual display configuration).

Two other suggestions:
1: Reset the preferences. It’s amazing how many different issues seem to be related to that.
2: Disable the use of the GPU in Preferences - Performance. The GPU is now used for other things than just the develop module, so it just might be the problem.

OK. Question answered anyway. The problem is elsewhere.

Adobe can’t possibly know what all plugins do or don’t do. The changes of version 7.3 in the develop module for Dehaze and camera profiles could very well break a plugin, and it’s up to the plugin author to check that and do something about it.

That would be bothering, to say the least. Changes in LR that make plugins incompatible should be advertised, especially in a minor release where they are unexpected. Anyway, disabling all plugins doesn't change anything.

So? A plugin that was compatible up to version 7.2 is not necessarily also compatible with version 7.3.

> You have quite a few plugins installed. Maybe one of them is the culprit.

I have these plugins since a long time. Never had this problem before 7.3.

Nobody says that I thought that you didn't believe me. Just wanted to give an example.