App seems to use mobile data despite setting

/e/ version: 0-9-o-2020051454222-dev-whyred
Device model: Xiaomi Redmi Note 5 Pro (whyred)
When it started to occur: unsure, first noticed a month ago
Reproducible with the last /e/ version: not tested yet
Reproducible with LineageOS: did not test

Summary

I will provide a screenshot.

In the settings for an app, I turned off "Background data" (described as "Enable usage of mobile data in the background"). Despite this setting being off, background mobile data climbed to 0.98 GB, apparently ignoring my setting.