Small files are listed as zero bytes

Version 5.5.5 contains a directory display bug where files of a small size (under 1k I think) have their size reported as zero bytes, on both the client and the server sides.

Reverted to 5.5.4.

I assume you refer to 5.6 or 5.6.1, not 5.5.5, right?
See https://winscp.net/tracker/1204