Integration behavior differs from UI behavior due to Absence Fast formula?

Summary:

We have an inbound integration with a third-party that sends us absence entries.

It was brought to our attention that the duration of absence come in as null instead of the actual hours that were sent.

After some analysis, the team noticed that a few absence types are causing the problem. Those absence types have a conversion and validation formula attached to their type attributes. Those fast formulas were designed to calculate the duration of an absence among other things.

Other absence types, come in just fine via the integration.

Also, when we submit an absence via the user interface, we have no issues and the duration are calculating correctly.