Advice on boiler flue

[Cmac9696]

Recently had the expansion vessel replaced in my boiler. This is how the boiler engineer left the flue. I’m not an expert by any means, a competent DIYer but this doesn’t look legit to me. what’s people’s thoughts?

 

[gas112]

Peel the tape off and take pics
Did he take boiler off wall to change it or do in situ

 

[Cmac9696]

Some more photos below after tape has been taken off.
I wasn’t home when the work happened, it was my partner. But the engineer did tell me the flue would have to come off to get to the vessel so I assume maybe he did take it off the wall?

 

[CountryFan]

Flue looks ok, hard to tell exactly just from photos. I think there’s possibly a screw missing though. Why in one photo are both boiler covers off?

 

[gas112]

Blowing up the pics he has not put the screws back in on elbows and flue extension .
it looks like its possibly not been lined back up as it was