In my recent manual builds, search has not been working (searching for something returns 0 results). I can only describe this behaviour as random - one time it was fixed with a simple CSS change (which was unrelated!) and then I tried different combinations of CSS changes which fixed or broke the search at random with no consistency. Right now I am at an exact state at which the search was previously working, but now it's not, and I don't want to keep tinkering with the CSS any further as I cannot figure out what is fixing or breaking it and it just seems random.
I'm using the latest update for RH2019 (New UI). The output I'm using is Responsive HTML5.
By the way, if I import the same project into RH2020, it works. Before I have to upgrade to 2020 I want to know if there is a way to fix this in 2019.
I'd do a test with creating a new Preset and using it to see if it misbehaves. Otherwise, since you're already on RH2019 New UI, going to RH2020 wouldn't be that much pain.