Contacts App — Can't Add Contact To Group

When Contacts is first open, I'm able to drag a contact card into a group, but that function stops working after that. The only solution I found is to restart Contacts (with or without holding the shift key), after which I am only able to do this again once, or twice if I'm lucky.

I should mention that all my cards are not located on my mac. They are all on iCloud.

Creating a new group only allows me to add cards into that group and not the others. It's as if the others are offline.

I would love to understand this a little better. Does anyone have a (better) solution than to restart Contacts every time I need to apply a group change?

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I realize this is an ongoing problem since 4-5 years ago. Creating a new post here in the hope to finally be on Apple radar.