shimano steps e7000 odo random reset

[vkcpolice]

Hi all I'm new to the forum so I hope I am posting in the correct forum. I have a merida e big 9 running the shimano steps e7000 system. I have only had it about a month and I have used it up to around 400km but when I went to show my brother the bike I had noticed the odo had randomly reset to 0. Everything else is still working fine. Should I be concerned? Is there any reason why this would have happened. Do you have to keep the battery in for it to keep memory as i had the battery out overnight while charging but never had this problem before. I am taking it to the shop today but I don't know how much help that will be as everything is still working other than the odo reset thx