ATEM Mini Pro Cache Full

Does using stills or powerpoints cause the ATEM mini pro to fill its cache.

The only thing that causes the cache to fill up is when the ATEM can't reach the CDN. Some CDN's when they see a static image will sense a super low data rate and think you aren't streaming.....if you do that for an extended period of time the CDN could boot you and that would cause the cache to fill up. When streaming you should always be monitoring at the CDN (and viewer) level IMO and not be relying solely on the ATEM Mini to tell you what's going on. If you see the cache filling up you likely are seeing stuttering on the CDN side.