off a load

19:02 Jan 23, 2018 

Oh, I don't doubt that for a minute; I'm just saying it is not "normal" usage in EN, and to some extent, the exact reason for using that curious term might influence the way you translate it! What is your current proposed translation?
I am suspecting it is actually an abbreviation for the name of some kind of document, like 'load platform docket', which would then of course put a completely different light on things! I assume also from your wider context you probably know what kind of 'loads' these are, and also, what kind of 'platform' is being referred to; in both cases, I suspect they will not have their 'normal' meanings!

16:56 Jan 23, 2018 

C'est le client qui m'a confirmé la signification de LP comme "Loading Platform" dans une traduction précédente... Aucun doute sur le sens de LP.

07:38 Jan 23, 2018 

You are parsing this incorrectly, which suggests you may not have fully understood the meaning of the source text?
The verb here is 'to leave something off' — in the sense, probably, of 'omettre'

Quite what an LP is must be specific to the organisation — usually, one might expect a load to be on a loading platform, so it's hard to see quite how the reverse might be the case.

I suspect this LP is perhaps some kind of document, like a 'despatch note', that is supposed to be attached to each consignment ('load'); so of course leaving it off, or applying the wrong one, would indeed be a pretty serious mistake to make.