Had a SureStop fitted for a few years. Came home last week to find the main body (not the pushfit ends) had come apart and flooded the whole house. Ironic given the fact that if I had not had it fitted the house would not now need new flooring throughout not to mention everything else! Given the damage water can do then even if these devices work 99% of the time it is not worth the risk.
How old is the unit? Just a bit worried now as I have one installed in my flat Don't think my ones looks like this, maybe been revisions?
Don't like them or trust them,would never have one fitted,known a few peeps who have had problems with them failing. https://community.screwfix.com/threads/sure-stop.146548/#post-1613363
It's certainly been in for over 5 years, I can't quite remember exactly. I have seen plumbers comment on them on other forums saying they have been out to ones leaking or simply not working when they need to. Others have said they have fitted dozens. New designs may or may not be better but in my opinion if I had any other fitted in any other house then I would be looking at getting them ripped out. The flood costs will run into a few thousand pounds in the end and months of hassle. If a device like this is not 100% reliable then there is no place for it. You may be lucky and never have a problem though.
Just taken a photo of my one in place. It was installed in 2015. Look slightly different to yours as has 4 screws securing the top section, on your one it has plastic retaining clips where one has broken. But the screws are cording on the top I installed one at the time as thought like everyone else a good idea, ans the first place I saw one was in a local housing authority flat.
Always seem a bit "plasticky " puts me in mind of the sort of gizmos you see in Betterware catalogues.