I have had two semi-hollow body builds (both basses) and both had the problem of one of the holes being not fully in the center block. Unfortunately. It's one reason (not the only one, alas) that both of mine have solid color tops.
The stop-tailpiece will not work if the posts are not solidly in the center block. So, your choices are to send it back or try to fix it. If the shipping is not too expensive that may be a decent option, but you will want them to make absolutely sure that the one they send you back does not have the same problem. Since the neck and bodies are somewhat matched, you might want to have them replace the whole kit. Since I am in the US back and forth from Australia would have been about the same as buying a new kit...so I have some experience, for better or worse, at trying to fix this problem.
The problem may be related to the neck is not being precisely 90 degrees to the body center-line. It may be one or two degrees south of that, resulting in the bridge hole being just north of the center block. Not a big deal as long as the holes are in the center block...but a big deal if they are not. I wondered about this when I saw your video but was not sure...but now that I have seen that a post-hole is off the center block...
Attachment 44173
I wasn't sure when I first saw the video, but now I wonder...the side of the upper bout should blend smoothly into the neck with no "step". It looks like there may be a step, which would could mean the center-line was skewed slightly clockwise when they were routing. That might not be a big deal (I had a similar issue on my
ESB-4)...
https://www.buildyourownguitar.com.a...ead.php?t=5339
...but the post being slightly off the centerblock definitely is a big deal. The post will not stay in place without something to hold its outer edge.
If you decide to keep the body you can glue a small piece of wood in on the side of the center block. I have one in my
ESB-4, and it has held well since 2016, so I guess it works ;-)
You need a piece of wood that is about 10 x 2 x1 cm. Slather the side that will be in contact with the center block and the top with tightbond. Slip it through the f-hole and hold it in place for 10-15minutes. That's long enough for tightbond to set as long as there is no tension on the wood. Then leave it for 24-48 hours to dry completely. Because of the curvature of the top, the piece of wood won't be flush with the top everywhere, but it will bond well to the center block. That should provide enough wood so that your ferrule has something to hold it laterally, even if there is a little gap between the top and the piece of wood.
This is doable, and I think it would work well for the bridge, which really just has downward pressure from the strings, so you are really just making sure the post does not shift laterally and the ferrule is tight enough so that you can adjust the post up and down. I am not sure how well I like this solution for the stop-tailpiece, however. The stop-tailpiece has string tension pulling it toward the nut so i would want it to be really firm.
Alternatively, you could plug the holes for the stop-tailpiece, and use a trapeze, like what I did with my
ESB-4. If you are really careful, the plugs would be mostly under the trapeze and you might still get away with staining.
I did something more radical with my Jazz/ES hybrid... Doable, and I ended up liking the outcome, but it insures that the top will need to be finished in a solid color.
Jazz/ES hybrid big round dowel solution is documented here...
https://www.buildyourownguitar.com.a...ck+gibson+body