Facebook has made the decision to refund some advertisers on its platform, following a bug that misattributed video carousel ad clicks as link clicks through to the advertiser’s site.

The bug, which has been fixed, occurred on mobile web browsers, not on desktop or in the Facebook app. It meant that advertisers, instead of being billed only for clicks through to their sites, they were wrongly billed when users clicked on videos in the carousel to enlarge them.

Facebook reports that the impact from a billing perspective was 0.04 per cent of ad impressions, due to mobile web making up a small percentage of overall ad impressions on Facebook in general.

Facebook has had several problems over the last eight or so months with its reporting of ad metrics. In September 2016, it was revealed that Facebook had been artificially inflating a key video performance metric by between 60 and 80 per cent. This was followed in November with the announcement that Facebook had been misreporting time spent reading Instant Articles, overstating referrals, miscalculating organic reach of Pages, and completely-viewed videos not always registering as such. A month later, despite improvements in some areas, Facebook admitted that some reactions to live video were misallocated, and that there was a discrepancy between like and share buttons via its graph API.

Following its problems with metrics, Facebook made the decision to allow for an independent audit of its ad data by the Media Rating Council (MRC) in February of this year.