we have the exact same problem. session count in shopify decreased by 60% overnight starting on March 17th. The decrease cannot be reproduced in Google Analytics 4 or Universal Analytics. Anyone from Team Shopify who can help with this?
I noticed a JS Error on our page and just checked your shop: http://www.babumilano.com/
You have the exact same error. Most likely this is the culprit. I will have our dev team look into this tomorrow. Hope this helps…