Switched to vaginal temping

I switched to temping vaginally this cycle. I started temping CD 6 and it’s now CD 9 and each morning my temp has been the same 97.45 - 3 days in a row. Could it be the thermometer? It is a basal one, and has worked for temping orally perfectly fine. The thermometer does not say it can’t be used vaginally. I have a brand new one ready to go as back up. Should I switch to the new one tomorrow morning? I usually ovulate close to CD16 so I’m not worried about missing ovulation quite yet. Thank you.