I run FossaDog (2020-11-15) from a USB stick and have an hard disk with my data connected to my pc.
When Fossa was started up, the disk was normally seen and it's partitions were mountable. However, after some time, Fossa started acting up in the form of either loosing partition informations (showing as unrecognized ) or loosing the disk access at all (it's device file in the /dev stop to exist)