In the case of a capacity test, care must be taken to ensure that no network interruptions may occur in the 24 hours prior to that. Here from the manual points 2.2 and 2.3:
Interruption of network operation also includes a functional test, even if this is only a short interruption. In some luminaires, the charge of the battery is controlled by the microprocessor as described in point 2.3.
If this detects a network interruption, a timer starts in the microprocessor, which counts it down 20/better 24h.
If this boundary condition is not observed, it may happen that a duration test is completed with an error, although the battery is still OK and has full capacity.