Eloquent query behaving differently in Livewire page

I'm using the following query to select posts to display

$posts = $this->category->postsPublished()
    ->whereNot(function ($query) {
        $query->withAnyTagsOfAnyType(['Guest Post', 'Press Release']);
    })
    ->when($this->year, function ($query) {
        $query->whereYear('published_at', $this->year);
    })
    ->when($this->month, function ($query) {
        $query->whereMonth('published_at', $this->month);
    })                
    ->with(['author', 'tags', 'media'])
    ->orderBy('created_at')
    ->paginate($this->perPage);

When I run the query in Tinkerwell connected to the production server, it behaves as I would expect and filters by the year (or month and year) depending on the parameters passed to it. When it is run in the render function of my Livewire page the filtering appears to be ignored. I have verified that the $this-year and $this->month values are correct on the production server and tested the Livewire page on my local development server (it seems ok there but I have a limited set of data there)