Properly merging large geometries without leaking memory

[NakedDevA]

Hi, I'm converting a threejs project to use react-three-fiber. My project is a scene which renders a large number of objects (~80,000), so I merge them where possible, which is performant but memory is still leaking.

I saw a similar question and have followed a similar approach with usememo for the mergeBufferGeometries.

Here's my component: (With this component removed, the app isn't leaking)

import * as React from 'react'
import * as THREE from 'three'
import { mergeBufferGeometries } from 'three-stdlib/utils/BufferGeometryUtils'
import { LevelJson } from '../typings/types'
import { LAYERS } from './client'
import { LandmarkIndex } from './landmarkParser'

interface MergedLandmarkProps {
    levelJson: LevelJson
    landmarkIndex: LandmarkIndex
}

export default function MergedLandmarks({ levelJson, landmarkIndex }: MergedLandmarkProps) {
    const allLandmarks = levelJson.landmarks

    const geomsToMerge = allLandmarks.flatMap((landmark) => {
        const sharedGeom = new THREE.BoxGeometry(3, 3, 3) //placeholder

        return landmark.entries.map((entry) => {
            const geom = sharedGeom.clone()

            const rotateQuat = new THREE.Quaternion()
            rotateQuat.fromArray(entry.q)
            rotateQuat.normalize()
            const matrix = new THREE.Matrix4()
            matrix.makeRotationFromQuaternion(rotateQuat)
            matrix.setPosition(entry.x, entry.y, entry.z)
            geom.applyMatrix4(matrix)

            return geom
        })
    })
    const merged = React.useMemo(() => {
        return mergeBufferGeometries(geomsToMerge)
    }, [geomsToMerge])

    geomsToMerge.forEach((geom) => geom.dispose())

    return (
        <mesh geometry={merged!} layers={LAYERS.Zones}>
            <meshPhongMaterial color={0x3a3c42} flatShading />
        </mesh>
    )
}

The other linked question implied that a geometry set as an attribute would still be managed, but when switching levels and returning to the same set of landmarks, heap size keeps increasing.

Are there any changes I should make to improve this?