router external storage

Hi, I recently got a couple of My Book 4tb drives to hook up to my AX88U as network backup for my photos and documents. After adding about 2.2tb of files onto them, the transfer throws an error and stops. According to the web interface, the drives indeed still have ~1.5b free. My drives were...

My Blue Cave router Traffic Analyzer never shows traffic statistics for more than 3-4 days back when I choose "Show by monthly". I suspect it's the lack of internal storage causing the older data to be deleted. I hoped the USB drive would allow for more data stored but it didn't and I couldn't...