Problems with Go 530T

After the most recent update I have encountered two major problems:

1. The device keeps switching itself off and then on again. Sometimes
it remembers the route it was following, other times not.

2. The speed limit of the road I'm travelling on shows as 59 instead of
60 or 71 instead of 70 !

Anyone else had this/these problems ?

I will, of course, get on to TomTom but there seems to be some very
knowledgeable people in this group who will probably reply a lot faster.

Walt