Hi Geoff, it doesn't appear that this question has arisen before on the forum, so it's not surprising that no one can give you a quick answer. As it's a general Android issue (not B4a specific) you'll probably find the answer quicker by Googleing the problem. In fact doing that, there are half a dozen things to try on the first page of results.
As I can't recreate the problem I can't try them out and give you a definitive answer, so give it a go and let us know how you get on.