Alright, sorry for this very late reply. I installed HDDriver 10.03 and updated the CosmosEx.
Unfortunately nothing much changed.
Regarding the problems copying big files:
Tried to copy a 12MB file from the IDE to the SD using TOS copy. Copy operation failed with an error dialog.
Regarding the problems with unpacking files on a shared network drive:
Tried to decompress some LZH files that I put on the shared network drive. Some of the files fails to unpack when decompressing using LHarc 3.10 junior (TOS program). Fails at the same place every time. However, when using LZHShell 3.10 (GEM program) it works. The very same LZH was also successfully decompressed using WinRAR on Windows on the shared drive. So, the way LHarc 3.10 junior (LHARCENG.TTP) writes/reads data triggers a bug in CosmosEx I guess. I've had the same problem with ZIP files, using ZIPJR.TTP (TOS program) would cause errors when decompressing, while using STZIP (GEM program) would work just fine. If you want I can send you the LZH files that triggers this bug Jookie. The very same LZH file works to decompress on both the SD card and the IDE drive, so I guess this bug is specific to the shared network drive.