Now that I did not know. Installing Packs in the same order they were deleted can be a guessing game. Yamaha needs a way to save a backup of Expansion Packs so that they can be reloaded in the correct order for registrations to work properly.
I always assumed that registrations were a direct link to styles, sounds, DSP's etc. and would work as long as those styles, sounds, DSP's, etc were available to link to a USB or user memory files. Why should it make any difference when those style packs were reloaded?
I agree that Yamaha must make it easier to Backup what we have in YEM. But there is a way to do it in a workaround, I explained in a video I linked in a previous post.
When we enter a new package in YEM, it is inserted into the first free bank (LSB). If there is no PACK in YEM, then they are installed in the order in which we enter them - 000, 001, 002 ... This order is important if we used Registrations that call some content, Voice, Style, Multipad ... Let's say Registration # 1 calls MyStyle01 located in the PackCasper that is installed in the first position (LSB = 000). And we deleted PackCasper and entered a new PackLeonB. PackLeonB will be positioned at LSB = 000. Registration # 1 cannot find MyStyle now, Registration is invalid. We now insert PackCasper but its 000 location is no longer free and it is placed on the first blank LSB.
I hope I was able to explain why LSB is important. The position of the Pack can also be changed later, here is how.
Change Bank select LSB