Bite marks at top of both sleeve crowns

I took the sleeves off and sewed them by hand. I also added a strip of body canvass to add an extra layer as the cloth is very light weight and turned out much better.

How did it turn out?

Maybe try putting your ease in the sleeve before basting them to the jacket using a couple rows of stay stitching.

Kinda looks like the needle deflection tho

This was King Charles today in his new Henry Pool suit - he appears to have the same issue you have... Judging by the creases it is a linen or linen mix suit.

First off - I think it looks great. Linen is a very difficult fabric to shrink, but I dont think that is what this is, I think you have used a two thin / blunt needle that has deflected whilst sewing. I always hand stitch sleeves in with silk thread and a 2mm back stitch cos I work with heavy fabrics and I get this a lot - commercial needles are shorter so flex less than domestic.

Solution - You could try lots of steam and hand shaping???

I don't imagine it's going to be anything as simple as this, but – sometimes when sewing through multiple layers of linen (e.g. pocket welts) I have found that because the fabric is so hard/stiff the needle can fail to go through completely straight – so a straight stitch on the top side can come out wonky on the underside. Did you check both sides of the stitch were straight?

Ps for what it's worth, I think the coat looks great!