Getting delayed 400 error. Tax prices are inconsistent

We are using SM8s API to integrate with our quotation software and are able to create a quote and edit it no worries, however we leave it for some time. Not sure how long exactly, its usually a day or so in my instance. And we receive an error back from SM8 when trying to sync the same data to them, that was accepted days earlier.

{"errorCode":400,"message":"inc-tax and ex-tax prices are inconsistent. Expected price [$159.09]."}

Now my quote had a single item in it and was for $175.00 so it’s clear that the tax (GST) is the difference in the values… but I have no idea why this is happening and why is it delayed?