I don't have any devices with android above 8 version at the moment, so I can't help with testing, but so far I've never encountered any problems or complaints from users regarding my Google achievements, and all I do is unlock them, without verifying if they've been already unlocked or not.
Basically, whenever the right conditions are met (even if that happens multiple times), I unlock the achievement and I copy paste its id from the developer console. By the way, are you sure that you have the proper achievement id in your events? I'm seeing that your achievement in your screenshot has a dash (-) in the middle, while my achievements all have an underscore (_) in the middle. It would seem really strange if your achievement ids were so fundamentally different from mine. Here is an example of one of my achievement ids: CgkI8dOq_4wIEAIQAw
If you wrote the id by hand, by any chance, you can click on the achievements in the google play console and then you can copy paste the id so that there are no mistakes. You say that it used to work before, so if there really is something wrong with the id, could it be that you changed your code recently, when you started having these issues?