Issue with Misalignment in 3D Printed Split Joint

[lukasdobis]

Hi, I would need some help with modeling a joint for 3D printing, for a model that will be larger and cannot be printed as a single piece on the printer.
I found this video: https://www.youtube.com/watch?v=zI8OgRRF5d8&ab_channel=NeedItMakeIt where it shows and prints this in practice. I chose the angled version also because of strength, mainly for the frame that I want to print.

The problem I have, and need help with, is correctly modeling the joint along the cutting plane through the part. I can’t figure out how and why in his model it fits perfectly, while in mine there is always a misalignment along the plane where the cut is made. I’m attaching both files and would really appreciate any help and explanation, so that I can model this type of joint correctly on other models as well.

Thanks in advance to everyone!

[Warmingup1953]

Is it this angled plane is at 45 Degrees, not 30?

[lukasdobis]

Thank you for your response. Yes, setting the value to 30 resolved the issue, but something interesting happened the first time I made the change, and I haven't been able to replicate it since. The person in the video also has this effect in their project. A kind of shadow appeared under my object, and when I moved the mouse over the construction plate, half of the object was displayed, as if it had been sketched there. I then traced it in red. Could someone explain how this works? It would be fantastic if I could use this feature consistently.

[TheCADWhisperer · Accepted solution]

Oops, I pointed to the wrong Effect, but I think you get the idea.