I’ve seen a similar post on the 255 forum about graphical artefacts and glitches.
I am having a similar issue on my fairly new 245 Music.
It can be cleared by changing screens but then will come back later on - sometimes quickly sometimes I don’t notice it for a few hours.
I have tried powering on and off but it still happens.
I’ve attached some screenshots below.
keen to know if this is a know issue which will be addressed via firmware updates in future. Happy for Garmin support to contact me directly if needed. I’m based in UK