Df-Messenger Dialogflow not presenting chat-height & chat-width and allow-fullscreen is oversize

Question

I'm trying to deploy a Dialogflow CX bot using df-messenger, and its been great apart from on mobile it presents really badly.

Allow-fullscreen="Small" takes it fullscreen on mobile, but it presents as bigger than full screen. Initially when the bot opens it firs the screen perfectly, but then as soon as you key text into the bot then for some reason the presentation window expands outside the visible screen, meaning that you can no longer see the send or minimise icons.

I'd prefer to use this fullscreen, but it needs to not then grow beyond full screen as soon as you put text in. Alternately I guess I could in theory control the chat window size by using the chat-height and chat-width attribute as shown in the google documentation, but the trouble is these do precisely nothing - as I have implemented it at least, either on desktop or mobile.

Does anyone know how to fix this please? I'd be very grateful.