When using local drives it is fairly common that the folder exported is that of some local media (e.g. USB stick). However removing that media often requires unmounting it to make sure everything is flushed, and the file system is left in a clean state. This is currently very cumbersome in ThinLinc (at least in full screen) as you have to switch from the client to the local system to unmount the drive.
We've largely relied on the OS mounting the media in some form of "sync" mode, where it can always be safely removed. This isn't always true though, and doesn't solve the issue of waiting for all data to be written though as it lacks feedback to the user.
We've gotten reports that Igel stopped doing "sync" mounts so that this is now a big issue on those terminals.
We also had a report that Igel had mentioned in their release notes the rationale for removing the "sync" option.