I bought one of these for DS (a little above his age range but meh) and he loves it.

BUT

Every time we go to refill it for him, or wash it at the end of the day, there is a slimey mouldy substance on the inside of the cup, lid and valve ... he only drinks water from it (he only has water, boob or the occasional milk to drink)

We haven't had it with any other cup that he has used. I've contacted Tommee Tippee and awaiting a reply to see what they say, not that I know what they could do anyway

Has anyone else encountered this issue?