Wrong time in NUKI Web

Actually, we have a service using NUKI API to get a code from every time our clients ask for it in order to be able to unlock the smart lock on the ordered day/hour.

Everything works fine but not the hour in the Web Nuki.
For example:
A client wants a code to unlock the SmartLock on

15.04.2021 from 13:00 to 17:00…
On our side, we do what has to be done (see image to see the code used) but, when our clients tried to unlock at 13:02, for example, it does not work.
It happens to our clients, so we looked all over to search for the problem and we observed that the info is stored in the Web Nuki with different hours from what we sent. In this example, it is stored from 15:00 (instead of 13:00) to 19:00 (instead of 17:00).

This 2-hour difference seems to be a constant.

For info, the lock is installed in Switzerland, our server is in Switzerland, and the clients are also in Switzerland

Can you please have a look and give some feedback.

I assume you set everything in UTC?
Did it work for you before and suddenly change or may this already be the case for some time?