Exporting of instant recordings do not always work.
BTW Streaming of the instant recordings that fail to export fail as well.
Unless you stream or export instant recordings you will not notice the bug.
I've tried streaming and exporting of instant recordings and have, so far, only found the problem you describe on the other thread with rewound instant recordings (if that makes sense?).
Let me describe a solution that worked for me, at least with SD recordings. [Further edit: worked with HD as well]
I have done this using ftp, but you may be able to do something similar by exporting to USB drive. You will probably need to use ftp for part of the "solution". This could be very tedious for a big file. Needless to say, we shouldn't have to do this but...
Using ftp you will find on your Humax a directory called (for example) Family Guy_20141025_2343.ts - inside which are files chunk.0, chunk.1, chunk.2 etc. Copy all these as they are to your PC. Forget chunk.0. On my PC (running windows XP!) I did the following. Open a command window in the directory you stored the chunk files and then do a binary copy/append of the files (eg. copy/b chunk.1+chunk.2+chunk.3 xxx.ts). Obviously, if there are many chunk files this becomes a pain, and you might have to split the copy (perhaps copy/b chunk.1+..+chunk.10 xx1.ts , copy/b chunk.11+...+chunk.20 xx2.ts etc and then finally copy/b xx1.ts+xx2.ts xxx.ts). [EDIT: Make sure you add them in the obvious numerical order!]
Back in windows itself rename the xxx.ts file to "Family Guy_20141025_2343.ts". (I needed to do this because a dos shell couldn't cope with the spaces in the filename). Note that this recording is unplayable on your computer and needs to go back to the Humax for decoding.
Use ftp to delete or rename the ".ts" directory on the Humax and then ftp your new file back.
Check to see if the Humax will play the recording. If it does, the method has worked. If you need to "Foxy" the hmt file, do so. You should now be able to save the recording to a USB - and, on a good day, you might be able to stream it.
If you have a short recording that you can't save, try this method and see if it works. As usual, backup your work in case it goes wrong. If it does work for others, perhaps you could let people know the relevant command for other versions of Windows and other computers.
I think I might have to look into a way of automating this!