"DELETE ALL" button not deleting all files on printer

OS: Windows 10 Enterprise 64 bit 20H2 19042.1288
Z-Suite version:
Printer: M300 Plus
Firmware version: 2.5.11

For a printer with multiple stores files, when clicking the “DELETE ALL” button only 1 file is deleted.
Re clicking this button deletes an additional file, but not all files.
Disconnecting and reconnecting to the printer after clicking the button still shows files, so it is not a matter of the shown files not refreshing.

Before and after clicking the button: