Can’t speak for the OP but when I added a second Arlo Q several months back it didn’t setup properly from just using the add option for the device. The only way i got it to work right was to completely remove all of the Arlo related stuff and then add it back.
To say it isn’'t ment to be removed is a bit of a mis statement. All Smartapps can be removed if needed. It can and should be as a possible troubleshooting step if it gets to that point. It is just a drastic step.
In my case i did add them back to Smartthings. My issues was not a issue with them being in smartthings, but that at the time i didn’t get the default Smartthings mode and for some reason the camera was acting a bit off.
That said I just added two Arlo Pro 2 cameras and a base station yesterday and they appear to of add with no issue at all. So who knows what the deal is.