The reason for this is that the start and length and xfd parameters work across all the slots of the sampler. There is only one start and length value calculated using the parameter and the length of the longest sample loaded.
In the previous implementation start and length would be calculated using the length of the sample in the slot, so the result was that a start of 0.3 and length of 0.4 for example would mean something totally different per sample slot, so start and length would jump all over the place as you paged through the sample slots.
There was confusion about how this worked, as reported here in the forum, so I changed the implementation to what it is today. We really thought hard about how to handle this and decided on using the length of the longest sample loaded to draw all the samples, drawing an empty region where necessary to make it clear that if you moved start/length it might end up in an empty region in one or more of the sample slots.
I could simplify the sampler module by removing the slots, so there is only one slot, and then there is no need to draw empty regions and the sample always fills the entire display. There will then only be one gate input and no 8 individual gate inputs (which was implemented before and requested by @SSPix @tiger001 and possibly others, to facilitate situations where you need percussion samples and want to load them into one sampler instance).
Additionally by removing the slots you will have less creative possibilities IMHO and might have to build some of what you now have in the patcher yourself.
I think that is a job for a simple delay module and from what I remember that is one of the modules that we were going to implement as part of the KS. Of course, getting to the implementation of those modules depends on how much other UI or workflow tweaks that have to be implemented