Shims under garage flat roof joists

[Tom12345678]

Roofer has just finished replacing our garage roof. He has used shims to level the joists, but they don't look very well secured, and one or two are already either loose or have fallen out leaving the joists unsupported. I am worried further ones might come loose with movement over time. I have just had the invoice from the roofer for the completed job. Should I be asking for something to be done to improve the shimming? Could it be as simple as just using adhesive to secure them? Or is a different solution needed? Thank you very much for any advice!

 

[Wayners]

That's terrible.
Not my area tbh but those are window packers.
I have packed roof trusts with slate.
Normally you have a wall plate (wood) held on with roof straps.
Joists are nailed on to wall plate.