DeLonghi Pinguino

I have a DeLonghi Pinguino CT300 portable air-conditioner which I have just used for the first time for a long time. When it has been going for a few
minutes and has cooled down it begins to put out a spray of water from the outlet grill at the top front. I suspect that a drain tube down to the collecting tray is blocked. Question: how to get the top front cover off to have a look? Has anyone done this and can anyone confirm or deny my provisional diagnosis of a blocked tube?
Many thanks,
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