This seems to happen when the device goes to sleep (and there are items in the cart), and the Shopify POS app is reopened, the Subscription POS Tile does accurately reflect the current state of the items in the cart.
This is occurring for our POS Extension for Subscriptions. We subscribe to cart changes based on the Shopify tutorial for POS Subscriptions. In fact, the Shopify POS Subscription extension has the exact same issue.
To fix it, an item needs to be removed/added from the cart, and then the Tile correctly updates.
Package versions:
"@shopify/ui-extensions": "2025.10.x",
"@preact/signals": "^2.3.x",
"preact": "^10.10.x"
API version: 2025-10