Pete - hopefully you have already figured this out at this point.

But if not - import error troubleshooting 101 is "try to enter the data manually, and see if the error recreates, and if it does, see what data you are missing"

My GUESS would be that you are importing products that are Stock / Lot / Something managed in their ITMMASTER records, but you are not importing that information with your file, and X3 wants it.

If that turns out to be the case from an attempt of manually receiving the products or from an investigation of the product setups, hopefully you can map the data into the STOJOU map details and try again.

Good luck!

You need to change the setup of the entry transaction you used for import. I guess you are using the SMR import template.
1-Identify the entry transaction you are using: either it's in the import model or I think it's STD by default

2-Modify the misc. receipt entry transaction (on the Stock Tab) > untick all fields in the lot block:

Note: as the standard import template is a simulation of a manual entry, you can try first to create stock manually and check that this message is no more active.

I would add a bit - this message appears, because in transaction entry are required to enter additional values, which aren't included in the import. To avoid it - check transaction entry - remove unnecessary fields.