Antenna Connector on 900 450i Yagi Came Off

Yesterday, when I pulled the black cap off one of the antenna connectors on a 900 450i Yagi, the entire connector came right off.  We pulled the shielding back, pushed the connector back on, pushed the plastic sleeve over it, and then crimped it to make sure it stays on, and it seems to be working fine.

My question is how those connectors are supposed to be on there.  The other connector didn't appear to be crimped, so does it just rely on pressure from the plastic sleeve to hold it on?  Should the shielding be soldered to the connector before the plastic sleeve is put on?  It seems to me that would lead to a much better connection.

Can you share any pictures?

I didn't think to take a photo of it in the moment, but here is what the connector looks like prior to assembly from a Google image search: