inconsistent shape count

I recently got the warning that my grid was reaching its maximum number of physical shapes. I went into a cockpit and checked the grid info and found that I was at about 65,500 physical shapes, so I've been trying to figure out how to reduce that number and give myself some wiggle room to continue building. However, the physical shape count seems very inconsistent. I tried removing some blocks to see how much it would reduce the shape count, which it did, but when I replaced those blocks I had even more shapes than before I removed them. I tried this with some other blocks and found that my shape count kept increasing whenever I'd replace blocks.

I then tried building a test platform to figure out the shape count for certain blocks. I basically just built a large square of light armor blocks along with a cockpit. The shape count for this grid was 5. I tried adding some blocks, both vanilla armor and custom mod blocks. Not only did the shape count seem to increase by 3 for a vanilla light armor cube, and only 1 or 2 for mod blocks of any sort, but the shape count would sometimes not go down whenever I removed these blocks. For example, I removed all of my test blocks, but even after they were removed, the shape count for my test platform was 21 instead of its initial shape count of 5. I tried saving the platform as a blueprint and then pasted a new one next to the original. Now the original platform has a shape count of 21, but the new one I pasted has a count of 5, even though both platforms are identical.

My problem is that any time I place a block, the shape count increases inconsistently, and if I remove that block and replace it with something different, the shape count just keeps increasing, even if the total number of blocks in the grid stays roughly the same. It's like the engine doesn't recognize that anything was removed.