- MicroUSB for power - limits you to 2A, very bad
- Crap/slow eMMC - Look at random I/O as main method of judgment
- USB Hubs where they shouldn't be needed - OrangePi+ 2 made this mistake, get OrangePi+ 2e instead
- Poor board thermals - a good SBC will have a copper layer below the SOC to spread the heat across the PCB
- Non-mainline support - It might be great hardware, but its a dud without software
- Bad Power Supply - A phone charger is not a SBC power supply
- Slow MicroSD - Buy Samsung Evo 32GB cards, test immediately. Even with a good brand like these, 2 out of every 5 won't even do 10MB/s of write, or 2MB/s of random I/O, making them not a class 10 card. Exchange the bad ones, buy used if your on a budget.