I need this drive to be also compatible with windows in case my RPi / LE fails.
"IF" your RPi will die (RPi's never dies
), you can boot your PC from a USB stick and live-linux (any kind of Ubuntu) and save your data from the EXT4 formatted disk. That's isn't a real problem. If you have linux (LE) and want stability use a linux partition.
This problem was not occuring when I was still using Odroid C2 with the same HDD and older version of LE, so maybe there's something there.
Nobody said isn't exist support for NTFS at all under linux. Just not guaranteed. Sometimes it's weak, sometimes enough (or it looks like enough for you).