u/CupcakeCompetitive89

TLDR - What’s the feature at ‘A’? A big hole? Do ‘A’ and the cracks suggest I need a liner? We plan to use the chimney for 5 more years.
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I’ve attached screen grabs of a video inspection of my flue. It’s the oil-burning boiler flue—there’s a fireplace flue in parallel. 65 year old house, boiler is very clean burning, stack is in good shape. The entire chimney is behind drywall except in the attic and basement.

I’d like opinions about the cracks, which are limited to a short section below grade.
The technician told me the cracks aren’t bad and I don’t need a liner. His company installs liners. Most of the flue tile looked clean and without issues.

Also wondering what that feature is marked with a question mark.

Our furnace tech tells me we have an excellent draft and very clean boiler.

Yesterday I tried my hand at the repointing process. Removing old grout was a breeze/-and very satisfying—with angle grinder and tuckpointing blade. But I encountered loose bricks on the top two layers, a series of overlying cracked bricks on one corner, and I’m now thinking about pouring a proper crown instead of recreating the little sloped cap that was there. I’m worried about this “little job”getting out of hand—my goal was to get things water tight and stop water from running down the exterior in the attic.

Should I replace the cracked bricks or can I leave them? I don’t really want to have to demolish half the chimney.

Once the half dozen bricks are re-laid, would you build a form and pour a proper crown? Or can I get away with a low-profile sloped cap that doesn’t extend beyond the brick face?

Photos: 1) after, 2) cracks on corner, 3) before.