There are a few issues at play here. As has been mentioned the handcuff position is one. The back to back is easier to get on but allows movement, The rear stack is trickier and not everyone can be put into it successfully as such there are various improvisations that could have happened.
There is mention of special constables being involved. With the best will in the world they are volunteers who are barely trained and don't see the daily grind of regular cops and don't come across as many dangers.
The searching is going to be hugely scrutinised both at the time of arrest and the process attempted in custody.
There is also the firearm used. Good quality handguns are still hard to come by, however there is a growing market of converted air guns and starter pistols. The issue with these is that they are hugely unpredictable to use and you are in as much danger pulling the trigger as having it pointed at you.
The death of an officer in England and Wales has been coming sadly. Due to a perfect storm of media scrutiny, social media keyboard warriors as well as police management scared to upset community panels and meetings.
Officers are reluctant to use their powers to stop and search and 7se of force. They are wary of being dragged over the coals for perceived discrimination