I just upgraded my home wifi mesh system to wifi 7 by replacing 2 * XE75 Pro, 2 * X50 by 4 * BE65 Pro.
I kept my two X50-Outdoor. All the AP are wired through 2.5gbit switch

The system is running in AP Mode.
I can see from time to time that my devices have connection failures to website or streaming service like Neflix/Prime/HBO or MyCanal.
Speedtest from phone or pc fails randomly with connection problems. 
I tried all the BE65 Pro using 2.5gbit device and everything is fast and stable using wired network connected to be65 pro.
The MLO is unusable, with a connection reported by Windows as > 5gbps up/down, I can never go above 1Gbs true network traffic. Using wired connection on same be65pro shows fast and stable speed.
Internal deco speedtest shows only 800/800.

During the system install, the firmware was older and I achieved far better throughput, I encountered these problems only after firmware upgrade.

What can i do ?

Here is a description of my wifi network topology

                    ┌─────────────────┐
                    │    Internet     │
                    │   (8Gbps ↓)     │
                    │   (800Mbps ↑)   │
                    └─────────┬───────┘
                              │ Fibre
                    ┌─────────▼───────┐
                    │  Freebox Delta  │
                    │                 │
                    └─────────┬───────┘
                              │ DAC 10Gbps
                    ┌─────────▼───────┐
                    │ Switch Linksys  │
                    │   LGS328C       │
                    │  (28 ports)     │
                    └─────────┬───────┘
                              │ DAC 10Gbps
                    ┌─────────▼───────┐
                    │ Switch 8 ports  │
                    │   2.5Gbps       │
                    └─────┬───────────┘
                          │
         ┌────────────────┼────────────────┼───────────────┼───────────────┼───────────────┐
         ▼                ▼                ▼               ▼               ▼               ▼
┌─────────────┐  ┌─────────────┐  ┌─────────────┐ ┌─────────────┐ ┌─────────────┐ ┌─────────────┐
│  BE65 PRO   │  │  BE65 PRO   │  │  BE65 PRO   │ │   BE65 PRO  │ │ X50-Outdoor │ │ X50-Outdoor │
└─────────────┘  └─────────────┘  └─────────────┘ └─────────────┘ └─────────────┘ └─────────────┘