Excel renames my formulas to different language

I am using Excel with Office 365. The settings are set to the Dutch language and I use Dutch formulas. But somehow after re-opening an existing document Excel changes some of the formulas in my file to English (not all). For instance =XLOOKUP (Since it is set to Dutch I use =X.ZOEKEN) changes to =_xlfn.XLOOKUP. But a forumla like =IF (Dutch: =ALS) hasn't changed. The new changed forumla of =_xlfn.XLOOKUP does not work. When this problem occurs I also can no longer use neither the Dutch function =X.ZOEKEN nor the Enlish function =XLOOKUP.

When I mannually install updates for Office 365 the problem often is fixed, but it reappears within a few days.

I cannot find anything similar online. Does someone know how to fix this problem?