Resorbing graft over implant after 4 months: thoughts?

I placed an implant with buccal graft covered by non-PTFE membrane and buried it 4 months ago.

Graft thickness according to CBCT was 2.3mm.

I took another CBCT 4 months later and the graft has resorbed to 1.5mm and I can see the greyness of the fixture through the gingiva. I’m pretty sure when I expose the fixture for second stage it will expose some threads.

Should I re-graft the site with more particulate bone graft ? Will it osseointegrate against the current graft?

Thanks for your thoughts!