RF Antennae clip / lock?

I replaced the back cover on my Z2 last week with the help of the iFixit smartphone repair kit, but the antenna became detached in the process. Getting it back on was very fiddly for a 42 year old with crappy eyesight, but I did in the end, sealed things up and tested, all good.

Unfortunately a couple of days later the mobile and data signal started dropping, and it's been doing so ever since, even in places I've never had trouble with.

It's possible to buy adhesive so I'd like to have another go, but I'm worried I've damaged the connection in the process. So I'm wondering if anyone knows how these are actually supposed to attach, is it a clip as I've assumed, and if so is it easily damaged? Should I solder it to be sure, and if so is there a risk I'll damage something else?