They are not true I/O errors. LhA just calls it an I/O error if it reads past the end of the file when it encounters corruption.
IDEfix solves MaxTransfer problems only while the IDEfix software is running. If you copy files before the software is started, restrictions of the Kickstart driver apply. And for that MaxTransfer is way too high. Files bigger than 128K are corrupted if MaxTransfer is bigger than 128K (= 0x20000 or 0x1fe00). It does not harm to set MaxTransfer to 0x1fe00 everywhere and always.
BTW, which file system is used for your Emulation partition?
