Amazon expects to receive latency information with each inventory update. If it is not provided, then Amazon resets latency to the default value (1-2 days).
Linnworks sends latency information to Amazon with each stock level update only if it is set up in Linnworks > Settings > Channel Integration > Amazon - config > Default Latency OR Product Based Latency. Only one of these options can be used at the same time, and if neither is set up, then no latency information will be submitted to Amazon and Amazon will set latency back to default (1-2 days). This is the default Amazon behavior for stock level updates via API, and there is nothing Linnworks can do to change it.
In order to set up latency to work correctly, you need to use either Default Latency or Product Based Latency.
The 'leadtime-to-ship' and 'Fulfillment Latency' attributes in LinnLive will only change latency on Amazon when the listing is created and when the listing template is updated via the listing tool. In order for latency to remain correct, it also needs to be configured in the Linnworks config.
* If you are selling on different Amazon marketplaces using the same Merchant ID and the same SKUs, please refer to this article for more information on latency settings: https://help.linnworks.com/support/solutions/articles/7000005175-is-it-possible-to-set-different-dispatch-times-product-latency-for-different-amazon-channels-